Borrowing this from Lance McAlister’s blog:

Aroldis Chapman was dominant in Milwaukee on April 27.
He pitched 1.2 innings, throwing 17 of his 19 pitches for strikes, and picked up the win in a 7-6 (10 inning) win that afternoon. That day he struck out Carlos Gomes with an 88 mph slider that followed a 100 mph fastball.
It was the 4th time he’d pitched in the previous five days.
Since that day he’s made three appearances.
Last 3 appearances
April 30: K, BB, WP, BB, BB, 2B, K, K
May 5: BB, BB, 1B
May 10: BB, HBP, BB, BB
He’s faced 14 batters with 11 getting on base.
He has not retired any of the 7 batters faced in his last two appearances.
He’s thrown 69 pitches with only 28 for strikes.
Total: 1.0 inning, 2 H, 8 BB, 3 K, 6 ER

So, John Fay addresses the issue:

It was second straight outing that he’s failed to retire a batter in. After 12 scoreless appearances, he’s given up six runs in his last three outings.

“Chapman struggling some to find the plate,” Dusty Baker said. “We’ve got to find a way to get his mechanics back in the sync. He’s throwing the ball great. It’s a matter of throwing strikes.”

Baker said Chapman will not be sent to minors to get straightened out. The Reds will have to make a move with Jose Arredondo shortly. But, again, Baker dismissed the idea of sending Chapman to Louisville.

“We’ll figure it out,” Baker said.

So, is it coincidence that since throwing 4 out of 5 days, Chapman hasn’t been able to find the plate with a GPS? He’s not just missing either, he’s pitching like Steve Blass.
I don’t understand how a manager can say “he’s throwing the ball great” when he’s lucky to be in the same zip code as home plate. Maybe that word doesn’t mean what he thinks it means….

Is it just mechanics? Injury? Fatigue? I have no idea.

And what should the Reds do with him?

I’ve made my opinion known; even before this, I believed he should be in the Bats rotation. As I said this morning on the recap thread, if he can’t get it done with a 7-0 lead, surely they won’t have confidence enough to use him against teams like St. Louis or Philadelphia in the upcoming difficult stretch of the schedule.

The problem is, the way that Dusty is using Bill Bray (basically for one batter), he needs 2 lefties in the pen.

Who do you call up if you send Chapman down? The only two lefties in Louisville that are on the 40 man roster are Herrera and Maloney. Would you make a trade to bring in another lefty for the pen?