I was flipping through a magazine the other day when an advertisement caught my attention.

The ad was for a product that promised me the ability to be able to slam dunk a basketball. All I had to do was I follow this company’s training program designed to increase my vertical jump and buy its specialized sneakers designed to build strength in my calves, presumably growing them into full-blown cows. 

Now, I’m about 5-foot-10. The only hoop I’m ever dunking on is one that says "PlaySkool" on the backboard. I might add a couple of inches to my vertical leap if I worked at it, but my physical limitations mean I’ll never Be Like Mike.

Even some of the best athletes in the world have their limitations to how much they can improve, and in baseball that might be especially true at a position as physically demanding as catcher. Certain aspects of catching—agility, footwork, hands, body control—can improve to various degrees, but scouts say that there’s a limit to how much room for growth they feel comfortable projecting a player in different areas. A 19-year-old catcher with a 40 arm on the 20-80 scouting scale might be able to improve his arm strength a tick or two, but he’ll almost never develop a 70 arm. A big, lumbering young catcher might be able to make some strides with his lateral mobility, but he probably won’t get much more agile with age.

"Mobility behind the plate, hand-eye coordination is pretty tough," said Diamondbacks farm director A.J. Hinch, who spent seven years catching in the big leagues. "Catching the baseball, you can soften someone’s hands a little bit, but I don’t think you’re gonna turn him into a Gold Glover if he’s got a couple of rocks on his hands."

General managers, farm directors, catching instructors and scouts talk about the importance of finding a catcher who not only has physical skills but who also possesses certain mental characteristics that they value at the position. That doesn’t mean a catcher needs to be able to understand mathematical physics or be able to explain the process of protein synthesis in the human body, but he should have the capacity to manage more tasks than a center fielder would. It takes intelligence—along with coordination and quickness—to understand how to block different types of pitches. A fastball in the dirt will bounce differently than a slider in the dirt, and the spin on a curveball from a righthander will make the ball bounce in a different direction than a curve from a lefty.

"They do not have to be fast down the line, but most good catchers are light on their feet and they move pretty well behind the plate as far as shifting to block balls," said Rangers farm director Scott Servais, who caught 11 seasons in the big leagues.

Among the official fielding statistics available for catchers is the passed ball. Like RBIs, passed balls are a teammate-dependent statistic, a function of a catcher’s individual skills, the opportunities given to him by his pitchers and the official scorer’s judgment. Passed balls happen when runners are on base, so if a catcher is on a team that doesn’t allow many baserunners, that reduces his opportunities to commit a passed ball.

In the major leagues in 2008, there was also a positive correlation between a pitching staff’s walks allowed and its catchers’ passed balls, even stronger than the correlation between baserunners allowed and passed balls. The correlation is partly because more walks means more baserunners (and thus more passed ball opportunities), but it might also be that pitchers with better control are less likely to miss their targets and create opportunities for the catcher to commit a passed ball. The most glaring example is a knuckleball pitcher like Tim Wakefield, who comes with his own catching caddy. So it’s no surprise that Charlotte and Pawtucket, which got 170-plus innings out of knuckleballers Charlie Haeger (White Sox) and Charlie Zink (Red Sox), ranked first and second in the Triple-A International League in passed balls.

It’s up to the official scorer to either penalize the pitcher with a wild pitch or ding the catcher with a passed ball, and one man’s passed ball might be another’s wild pitch. It’s especially difficult for minor league scorers, who often don’t have the benefit of instant replay, so we’re left with the uncertainty surrounding the discretion of the official scorer.

While pitchers and official scorers throw noise into the data, the catchers themselves might even muddy things up by creating a selection bias. If a catcher is excellent at blocking balls in the dirt, his pitchers might feel more comfortable throwing more pitches with downward action low and perhaps even beneath the strike zone with runners on base. But if a pitcher knows his catcher isn’t the most adept at blocking, maybe he doesn’t throw as many of those pitches with men on, giving the worse defensive catcher fewer opportunities to commit a passed ball.

In the major leagues, few players play a full 162-game season. Since 1999, the most games caught by a catcher was Brad Ausmus’ 150 games caught for the Tigers in 2000, though Russell Martin and Jason Kendall came close to that mark by catching 149 games each in 2008. In that same 10-year span, there have been 19 instances of a catcher catching at least 140 games, and a remarkable seven of those seasons come from Kendall alone.

So let’s use 75 percent playing time, which adds up to around 120 games, to look at the passed ball rate at each level of full-season baseball the last three seasons.

Those numbers are remarkably consistent and could serve as an indicator of league difficulty, as the industry consensus seems to be that the biggest jumps for players are from A-ball to Double-A and from Triple-A to the big leagues.

Catchers out of high school aren’t used to catching pitchers with 90-plus mph fastballs, breaking balls that break, sinkers with sink or changeups that even exist. By the time these high school catchers start their first year of full-season ball, they have probably gained experience catching professional pitchers the previous year in rookie ball, in instructional league and again in spring training, but it’s still an adjustment and one that must be made over the grind of their first 140-game minor league season.

"One of the things that comes for the youngest catchers is their strength isn’t probably where it’s going to be, obviously," Hinch said. "When you get into 17, 18, 19-year-old catchers, the strength to withstand the physical requirements of the position—and also arm strength and hand strength—their bodies aren’t at maturation yet, so you just want to get them a good base. You want to make sure they have the foundations, stances, ability to receive pitches well, footwork, all the basics. But it’s really simplified for the catchers due to their lack of strength. As they mature and as their bodies get involved, they can take on more and more work."

There appears to be no discernible difference between the quality of catchers’ blocking skills in low Class A compared to high Class A. There is, however, a reduction of six passed balls per 120 games upon the jump from A-ball to Double-A, which is probably a mix of catching and pitching skill. Compared to high Class A, Double-A is filled with more veteran catchers, players who might not be prospects but who can stick around and handle young pitchers. While the catchers are better in Double-A, the pitchers are also better and generally have better control as well.

There might be a slight difference between Double-A and Triple-A catchers, but the difference appears to be small, if there even is one. The two main jumps appear to be from A-ball to the high minors and from the high minors to the majors. Again, it’s probably a mixture of catching skill and a reflection on the control of the best pitchers in the United States. The passed balls per 120 games in Major League baseball broken down by team ranges from 3 (the Twins, led by Joe Mauer) to 13 (the Red Sox, which had knuckleballer Tim Wakefield throw 181 innings in 2008, and the Reds, who mostly used Paul Bako and David Ross).

Now that we know the baseline to compare players to relative to their level of play, let’s look at the catchers in the 2008 version of the Prospect Handbook—with a few other names sprinkled in—to see how they did this year. I should note that the PB/120 G column is not really passed balls per 120 games, but passed balls per nine innings multiplied by 120.

The Good

Matt Wieters: Wieters is good at everything. He hits, he walks, he hits for power, he controls the running game and he keeps the ball in front of him. There really isn’t much more to add about the Baseball America Player of the Year. He is awesome.

Taylor Teagarden: Voted the best defensive catcher in the both the Double-A Texas League and Triple-A Pacific Coast League, Teagarden has a solid case as the best defensive catcher in the minor leagues. He rarely allowed a passed ball and committed only two errors in the minors. He has all the tools scouts look for in a top-flight defensive catcher: an outstanding arm, quick pop times, good hands, athleticism and strong blocking skills.

Bobby Wilson: Wilson doesn’t stand out with any outstanding defensive tools, but his dedication to his craft, preparation and feel for the position make him a good defensive catcher. He’s a slow runner but he moves around well behind the plate. He gets good reviews for having a strong understanding of his pitching staff, enabling him to position himself well and keep balls in the dirt in front of him with his instincts and soft hands. His arm strength is average, but he got rid of the ball quickly enough to erase 43 percent of base stealers. Wilson has put up solid numbers throughout the minor leagues, though like all Angels prospects he’s had the benefit of hospitable hitting environments since leaving the low Class A Midwest League. At 25, his room for offensive growth might be relatively limited, but he could be at least a solid backup with the potential for a bit more.

Craig Tatum: Despite succumbing to Tommy John surgery three years ago, Tatum is now one of the best defensive catchers in the minor leagues. The Reds farmhand has good catching mechanics, records average pop times of 2.0 seconds and delivers throws to second base with a good throwing action, enabling him to nab 38 percent of base stealers in 2008. He controls the running game well, but he’s even better at keeping the ball in front of him, as he does a good job blocking and receiving and shows a knack for the finer points of catching like framing and calling pitches. One AL scout who saw Tatum this year projected him as a future regular, though he’ll have to improve his OBP after hitting .244/.297/.377 in Double-A this season. At 25, Tatum’s offensive projection is limited, but he has the defensive skills to at least get an opportunity as a backup.

Brian Jeroloman: Jeroloman signed with the Blue Jays as a sixth-round pick out of Florida in 2006. He’s a very slow runner—he has one career triple and has never even attempted a stolen base—but he moves well behind the plate with good footwork and agility. His hands work well and help make him a strong receiver. He’s formidable in all aspects of defense, getting out of the crouch quickly to complement his strong arm with a quick release to throw out 37 percent of runners this year. Jeroloman made his full-season debut in 2007 in the high Class A Florida State League, where he led the league with 85 walks and was second with a .421 OBP. He followed that performance by hitting a combined .252/.374/.369 with 58 walks and 64 strikeouts between Double-A New Hampshire and Triple-A Syracuse. Jeroloman made the Eastern League all-star game, but he is 23 and has shown little power in his career.

The defense is there for Jeroloman, but the power needs to take a step forward or the walks he draws because of his plate discipline will erode against more advanced pitching.

Pablo Sandoval: You’re going to have to forgive me. Last time I wrote that I’d go more in-depth about Sandoval here, but I’m going to save Sandoval for his own blog post early next week. Between his outstanding regular season—both offensively and defensively—and his monster winter ball campaign, there’s just too much to cram into this post. But as you can see, even though the Giants appear to be moving him from catcher to a corner infield position, not only was he serviceable and preventing passed balls, he was above-average in that department. 

The Bad

Adam Moore: From an offensive standpoint, Moore is one of the better catchers in the minor leagues. The 24-year-old Mariners farmhand hit .319/.396/.506 in 119 games with Double-A West Tenn this season—his second straight year with an OPS above .900—showing a short swing, solid power and a balanced stance that helps him stay back on offspeed stuff. He threw out 36 percent of runners with a strong, accurate arm and a quick release, but his footwork, blocking and receiving have been a constant work-in-progress and he’s not too agile behind the plate. And at 6-foot-3, 220 pounds, Moore is bigger than most catchers, though A.J. Pierzynski and Javy Lopez have had lengthy careers behind the plate at similar sizes.

Austin Romine: Jesus Montero is the frequent target when it comes to talking about Yankees catching prospects that might have to change positions, but Romine has some work to do himself to become an adequate defender. While Romine has an excellent arm, he is not a good receiver—at least not yet. He’s athletic, but his footwork is a work in progress. Romine’s sample size of 450 innings as a 19-year-old is small because he split time behind the plate at low Class A Charleston with Montero. Ideally, Montero and Romine would be split up next year so each player could maximize his games behind the plate, but that scenario might not be possible.

Welington Castillo: The 21-year-old Castillo batted a composite .287/.337/.383, mostly split between high Class A Daytona and Double-A Tennessee. Castillo has good defensive tools, most notably a plus arm. His blocking and receiving tools are solid, but they don’t show up with enough frequency yet, as it’s one of the many phases of the game in which Castillo is still relatively raw. With Geovany Soto still under the Cubs’ control for five more seasons, there’s little need to rush Castillo.

Koby Clemens: The Astros drafted Clemens out of high school with an eighth-round pick in 2005, the same year his father Roger was helping lead the Astros to the World Series. But after spending his draft year in rookie ball and two years with low Class A Lexington, Clemens had a modest .251/.341/.398 line next to his name in 1,005 plate plate appearances. Clemens was struggling defensively, too, committing 29 errors in 99 games at third base, prompting the Astros to convert him to catcher for the 2008 season. Though he was learning a new position and moving up a level, Clemens responded admirably by batting .268/.369/.423 in 109 games for high Class A Salem. A 21-year-old catcher who just outhit the Carolina League average OPS by 65 points is impressive, but Clemens has a ways to go on defense. The same lateral mobility and body control issues that plagued Clemens at third base hamper his defense behind the plate. He threw out 35 percent runners, but teams ran on him frequently because his pop times are below-average and his footwork needs improvement.