“It’s always risky with a hard thrower, right? Injury and all that?” the owner Hal Steinbrenner said in an interview before the start of the season. “But this is a guy that really has no injury history. He’s quite strong, and if anybody’s going to be O.K. for that many years, in that role, throwing that hard, it’s going to be him.”

So it had to be disconcerting when Chapman went to the disabled list in May for just over a month with shoulder inflammation, his first trip there for an arm injury in six years.

It could be that, even though he has maintained a chiseled physique, all the years of unleashing the fastest pitch in baseball — his fastball was once clocked at 105 m.p.h. — have begun to take their toll.

Even before Chapman’s trip to the disabled list, Rothschild said: “There’s a little difference in the command of the ball. It’s been more sporadic than I saw last year.”

That was particularly apparent on Friday night as Chapman struggled to locate his fastball, often sending catcher Gary Sanchez scrambling. But Chapman did not appear comfortable enough to throw his other pitches — his slider or his changeup — either because he was behind in the count or because he was concerned that a mistake could more easily be hit out of the ballpark.

All 23 pitches Chapman threw were fastballs. He generated one swing and miss.

The notion that Chapman should have incorporated his slider or changeup is complicated, Rothschild said, because Chapman’s fastball was not hit particularly hard.

“If he gives up a home run on a slider, what are you saying today? ‘Why didn’t you throw a fastball?’” Rothschild said. “That’s what he’s thinking ahead of the game.”