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CINCINNATI—Reds manager Dusty Baker is all for Aroldis Chapman letting his fastball flag fly.

"If you've got triple digits," Baker said, "you might as well use them."

Nobody hits triple digits as often as Chapman and no one throws more fastballs than Chapman. Chapman tops the majors in average fastball velocity at 97.8 mph, according to His swing-and-miss rate—18.9 percent—also leads the big leagues. Chapman has thrown 80.1 percent fastballs, 11.9 percent sliders and 8.0 percent changeups.

It's a formula that has worked well for the 24-year-old Cuban lefthander. Chapman's only hiccup this season has been a six-appearance blip in June, during which he gave up eight runs in 6 1/3 innings. Before that, he had not allowed a run in his first 29 appearances.

After getting back on track, Chapman went 15 outings and 14 1/3 innings without allowing a run while yielding just six hits and three walks to go with 33 strikeouts. Overall, he was 4-4, 1.89 with 96 strikeouts and 14 walks in 52 innings.

Chapman didn't remake his mechanics or change strategy to turn it around.

"I think the important thing he learned was that the mental resiliency is going to be as important as the physical," pitching coach Bryan Price said, "and that if he doesn't perform, it doesn't change the way we feel about him. Continue to go out there with focus and aggressiveness. What can you really do differently?"

Catcher Ryan Hanigan said Chapman's struggles were part of what everyone goes through. "You can chalk it up to the ups and downs of the season," Hanigan said. "He lost his command there for a minute."

Chapman is still doing what he did all year—being aggressive with the fastball. "He's still throwing a lot of fastballs and few sliders," Price said. "But he's still attacking the zone. He didn't get defensive. That's the last thing we wanted him to do."

The New 'Nasty'

Chapman's strikeout numbers are in rare territory. Through the end of July, he was  averaging 17.02 strikeouts per nine innings. The all-time best for a season (minimum 60 innings) is 15.99 by the Cubs' Carlos Marmol in 2010. Former "Nasty Boy" Rob Dibble is the all-time career leader at 12.17. Dibble's best single season mark was 14.1 in 1992 while with the Reds. In 115 career major league games, Chapman is averaging 14.6 strikeouts per nine.

Chapman's stuff is dynamic enough that he doesn't have to rely on strikeouts as long as he can throw strikes.

"What we're trying to do is not walk anybody," Hanigan said. "It's too hard to string together hits off him. He's not going to give up three, four, five hits in a row. He's rarely going to give up home runs. If he keeps guys off base, he's going to do his job. Obviously with velocity, he's striking out guys on a ridiculous scale."

It seems like anytime Chapman gets ahead in the count, it's pretty much over. According to

• He has been ahead 0-1 in the count 82 times, resulting in 11 hits, three walks and 50 strikeouts.

• He has been ahead 1-2 66 times, resulting in six hits, two walks 47 strikeouts.

• He has been ahead 0-2 37 times, resulting in five hits, zero walks and 29 strikeouts.

• He has had two strikes on a hitter 127 times, resulting in 10 hits, 10 walks and 86 strikeouts.

The ability to control his fastball and his secondary pitches is the key to Chapman's success.

"He has the ability to come in and out and up and down (in the strike zone)," Baker said. "He's feeling comfortable and very confident with what he's doing. And he's using more than just his fastball. Getting ahead helps to use more than just your fastball."

Future Considerations

When the Reds signed Chapman to a six-year, $30.5 million contract in January 2010, the intention was to use him as a starter. He was sent to Triple-A Louisville to start. After middling results there—5-5, 4.11 in 13 starts with 76 strikeouts and 40 walks in 66 innings—the Reds shifted him to the bullpen to help with playoff drive.

He spent last year in the bullpen and began the year with 12 scoreless appearances. A rough stretch that included 12 walks and just four outs prompted a stint on the disabled list, which the Reds used to remake Chapman's mechanics. When he returned, he no longer threw 105 mph—he has touched 102—but he has better command. He put up a 2.43 ERA over his last 38 appearances of 2011, walking 21 in 37 innings but striking out 36.

Given improved control, the Reds decided to try him as a starter again for 2012. He was set to make the rotation out of spring, but after injuries to closer Ryan Madson and set-up men Nick Masset and Bill Bray, the Reds shifted Chapman back to the bullpen.

"We needed him in that role," Baker said. "Where would we be without him initially in the set-up role and now as the closer? He's been involved in half our wins. I hate to think where we'd be without him in that role."

As for what's next, starter or reliever?

"We'll worry about that next year," Baker said. "We'll worry about that when we get (Ryan) Madson back . . . Once you've been a starter, most guys would rather start. Most guys didn't come up as a closer.

"He's getting better at having the same stuff the second day. Your body gets acclimated over a period of time. He trains hard, too."

While deciding his future role may be complicated, Chapman tries to keep the game simple. His off-the-scale fastball helps.

"Once we get two strikes," he said, "I go for the strikeout."