It takes an expert set of hands to juggle an organization's players around the four full-season minor league rosters. While farm directors and their assistants have a good idea of which players will populate which rosters before spring training even begins, they have to be ready for the unexpected.

Players get hurt; they have poor springs; others exceed expectations. So an organizational depth chart seldom looks the same in April as it did at the end of February.

Only one player can start at any one position on any given team. As such, a handful of players will earn higher-than-expected Opening Day assignments. Let's take a look at a few of those players in the Mariners and Padres organizations.

Padres

Righthander Simon Castro tossed five shutout innings, striking out five, in his Double-A debut for San Antonio. He toyed with low Class A batters last season, leading the Midwest League in strikeouts and making 27 starts for a 94-win Fort Wayne club that rolled to the league title. But the Padres resisted promoting him to high Class A Lake Elsinore so that he could "be part of the special season the Tin Caps enjoyed last year," according to director of player development Randy Smith.

"Castro was a slam dunk to go to Double-A with the way he performed last year and this spring," Smith continued.

Perhaps the most surprising Opening Day assignment, then, was that of Lake Elsinore third baseman Vince Belnome, a 28th-round selection last year out of West Virginia. He played a lot of second base for short-season Eugene last year, but he does not profile there—not on a regular basis anyway. "He's a little (raw) on defense," a Padres official said last fall.

Belnome, 22, garnered more attention for his offensive potential, batting .297/.431/.500 with 10 homers and 52 walks in 65 games for the Emeralds and earning a cup of coffee with Fort Wayne in time for their playoff run. A lefthanded batter, he hits to all fields, has just enough power and had earned official sleeper prospect status by the time instructional league was completed last fall.

"With his age and experience, and with the opening at third base in Lake Elsinore, it was a natural move," Smith said. "Belnome has a solid approach to hitting and should fare well in Elsinore. He is sandwiched nicely with (James) Darnell in San Antonio and (Edinson) Rincon in Fort Wayne, so again a perfect fit in Elsinore."

Joining Belnome in Lake Elsinore is righthander Jorge Reyes, a 17th-rounder last year who signed for $200,000 as an Oregon State junior. He compelled the Padres to act with a stellar Cape Cod League showing after the draft.

"Reyes has a great feel for pitching," Smith said. "He works fast, pounds the zone with a good sinking fastball and induces tons of groundballs."

In his first start for the Storm, Reyes came as advertised, inducing 14 groundouts and only one flyout in 6 2/3 innings of work. That's a distribution that comes in especially handy at Lancaster, where the game took place. Belnome started slowly, going just 3-for-30, but a 6-for-10 weekend boosted his average to .244.

Mariners

The Mariners jumped No. 2 overall draft pick Dustin Ackley to Double-A West Tenn, where he complemented an Alex Liddi/Carlos Triunfel left side of the infield. But all in all, it was an assignment befitting of a player of Ackley's stature. His start has not fit his reputation, however, as he was 4-for-36 through nine games.

A few other top college picks from ’09 landed with high Class A High Desert: first baseman Rich Poythress (second round), second baseman Kyle Seager (third) and righthander Andrew Carraway (12th). But the Mariners took it slow with the majority of their players.

Elsewhere on the West Tenn roster you'll find the system's biggest movers in a pair of 21-year-old international pitchers—one a tall righthander from the Dominican Republic; the other a 5-foot-10 lefty (and converted outfielder) from Venezuela.

Michael Pineda, the 6-foot-5 righty, and Mauricio Robles, the lefty, threw just 44 and 32 innings, respectively, in high Class A last season. Both earned their stripes in the California League playoffs, where they helped pitch the Mavericks to the league finals. Pineda struck out 10 and walked one over 10 1/3 playoff innings, while Robles fanned 13 and walked five over 11 1/3. Did the Cal League dominance influence the Mariners' decision to bump them to West Tenn?

"Not really. Both guys are prepared to pitch in Double-A," director of minor league operations Pedro Grifol said. "We have a lot of real good baseball people in our organization—good statistical people and good talent evaluators who've been in the game a long time. We lean on those guys a lot. It's a collaborative effort, but we usually arrive at a consensus."

Neither Pineda (six whiffs, three walks) nor Robles (five whiffs, two walks) allowed a run in his Double-A debut.

Hard-throwing righthander Maikel Cleto will help fill the void in High Desert, where he begins the season after making just eight starts for low Class A Clinton last year. The 20-year-old, acquired from the Mets in the J.J. Putz trade, missed spring training a year ago when he did not secure a work visa until June. Then he missed time with an oblique strain, making ’09 essentially a lost development year.

"He was one of the guys who came off the blocks very well," Grifol said. "His velocity was high, but his command continues to come and go. That's the one thing we're working on. But if any of these guys had command, then they wouldn't be minor leaguers. They'd be in the big leagues."