The first clue came on a simple toss back from the catcher in the fourth inning. Hiroki Kuroda snapped his glove at the ball. It was a small and uncharacteristic show of emotion from the Yankees' steadiest pitcher.
Kuroda did it again the next inning: Threw a pitch, received the return throw from Brian McCann and snapped his glove in frustration.
The pitches in question were balls. Kuroda wasn't upset with the umpire's decisions. He was upset with himself Saturday on a day when he didn't have his command or his breaking ball.
"I was trying to -- what's the word? -- suck it up," Kuroda said through his translator.
For a man who was the winning pitcher in the Yankees' 7-4 victory over the Red Sox, Kuroda didn't seem to enjoy himself much. Not that that's anything new for him.
In 2012, Kuroda admitted that baseball is more of a chore than a passion for him because of the ruthlessly strict way it was taught in his home country of Japan.
"To be honest with you, I never enjoyed playing baseball," he said then. "Rather than enjoy myself out there, I feel that I must fulfill my responsibility."
Kuroda's responsibility with the Yankees this season is to be a solid No. 2 and not wilt down the stretch the way he did last season, when he finished 11-13 with a 3.31 ERA.
Let's face it: Kuroda, 39, is the least interesting of the Yankees' five starters, even if he did correctly use American slang Saturday in a rare show of quote-ability.
Kuroda gets none of the start-to-start analysis of the fastball-challenged CC Sabathia. He doesn't provide the ups and downs of Ivan Nova. He doesn't have the comeback story, the big fastball or the obvious palm goo of Michael Pineda.
Even among the Yankees' Japanese pitchers, when it comes to salary and attention, Kuroda is the clear No. 2 to Masahiro Tanaka.
"I think there was curiosity about how CC would bounce back," manager Joe Girardi said when asked about his rotation. "You've got a young man [Tanaka] who comes over from Japan, who has never pitched in our country, and everyone's wondering how he's going to adapt. And then there was the question marks about Pineda: Where was he really at?"
Kuroda is consistently consistent. ERAs between 3.07 and 3.76 in each of his six previous big-league seasons. A career won-loss record of 70-71, which is shockingly mediocre considering how good he's been with the Dodgers and Yankees.
About the glove snaps: Snap No. 1 came after Kuroda fell behind No. 8 hitter Jonathan Herrera in the fourth before walking him. Snap No. 2 came after he fell behind Dustin Pedroia 2-and-0 in the fifth before giving up a double.
"My command, the precise control, wasn't there," Kuroda said. "So I was just trying to get the big outs."
Kuroda also slumped his shoulders after walking No. 9 hitter Jackie Bradley Jr. on four pitches to open the seventh with a 6-2 lead. After a strikeout and another walk, Kuroda was replaced by lefthander Matt Thornton to sustained applause from the sellout crowd of 48,572.
The two inherited runners scored, so Kuroda's final line (6 1/3 innings, six hits, four earned runs, three walks, five strikeouts) wasn't great. But the result was.
The inherited runners scored when Mike Carp grounded a ball to the shortstop position -- which happened to be vacant because the Yankees were employing one of their newfangled shifts.
For more than 100 years, teams played their shortstops at shortstop. Now that's not good enough. But that's another topic entirely. Shifts are here to stay, apparently. As Kuroda said, we all have to -- what's the word? -- suck it up.