Chapman, who began the season with 24 straight appearances without allowing an earned run, is 0-3 with a 10.13 ERA and two blown saves over his last six games. He gave up the decisive two-run homer to Asdrubal Cabrera in the bottom of the 10th for a 3-2 loss to the Indians on Tuesday.
"He got out of his delivery yesterday, and pitches that he was trying to throw in were running back out over the plate," Reds pitching coach Bryan Price said Wednesday. "He wasn't where he needed to be with his fastball command, and the velocity fluctuations we're probably sometimes just going to have to live with."
Chapman's fastball velocity, which can reach triple digits, was in the mid-to-high 90s, and Cabrera hit a 94-mph pitch for his homer.
Since becoming the closer, Chapman has relied heavily on his fastball and hasn't mixed in many other pitches -- like his slider. Price felt that a mix was good, but diversifying his lefty's repertoire is sometimes easier said than done.
"When he's on throwing with velocity and command, sometimes throwing a slider is taking a risk, only in the sense that he's pitching a lot of these shorter outings. He's not throwing as many sliders," Price said. "He could be more apt to maybe make a mistake with that pitch. When you have that type of velocity and command, you get a little reluctant to throw the slider. The aftereffect is, the less he throws it, the more foreign it becomes, too.
"When he does get a chance to throw it, as he did last night, it cut back and didn't do much. When you go into a one-run game, are you going to throw a pitch that you don't have great confidence in with a game on the line?"
Overall, Chapman is 4-3 with a 1.57 ERA and eight saves in 30 games.
"There are a lot of things going into the evolution of this kid," Price said. "As much as it's been fun to watch, there are always things along the way, like how he's going to respond to the hiccups he's had here recently."
Reds manager Dusty Baker hoped to get Chapman back on the mound as soon as possible.
"I don't care who you are, sometimes you're going to get hit," Baker said. "You knew it was going to come sooner or later. The real test of the life of a reliever is to forget yesterday. Now he'll have to pass another test and forget yesterday."