After striking out on a curveball from Ricky Romero in his first at-bat, Montero laid off the same pitch his third time up. He then hit another Romero curveball into left field for his first career hit.
"I think he's made some pretty good in-game adjustments," Girardi said. "I thought he had an idea of what he wanted to do up there, and that's a good sign."
Even though he is a September callup, Montero will see significant playing time at designated hitter on a team that is in a tight race for the American League East title and a near lock for the postseason. Being a rookie is hard enough, Girardi said, even with added pressure.
"You can throw all the other things out, just coming up as a rookie the first time," Girardi said. "It's not easy to relax. I think you want to impress everyone. You want to prove that you belong, you want an opportunity to come back the next year."
Montero, who has played catcher during his Minor League career, has an uncertain future at the position in the Majors. On Sunday, he received his third start as the designated hitter in four days. As the season winds down, he is likely to reprise that role.
"His work ethic is good," Girardi said. "He still does all his catching drills on days that he's playing, and that probably helps. And it probably helps being around some veterans that can help him in this situation. Still, you're going to be anxious."