Per Dave Cameron's tweet, here's Chapman's velocity chart from FanGraphs.
In terms of raw numbers, Chapman's average fastball velocity on Monday -- when he walked three batters in the 10th and threw just six of his 21 fastballs for strikes -- was 94.4 mph, his lowest average velocity in an appearance this season. Check his past three outings, according to ESPN Stats & Info:
Sept. 4: 98.0 mph
Friday: 96.3 mph
Monday: 94.4 mph
"He might be a little tired. He might have to rest for a while," Reds manager Dusty Baker said after Monday's game.
It's not an issue yet, but Chapman has been so dominant that two poor outings in a row -- with a significant decline in his velocity -- raises a red flag. I'm guessing we won't see him for a few days. Pay attention to his next outing.