"He said it grabbed," said Girardi. "I'd be surprised if he's a player tomorrow and I'm just hopeful that it's not much. We'll have to wait and see."
Ellsbury doubled and scored in the first inning and belted a go-ahead two-run homer in the third. His grounder in the fourth produced two more runs -- with the help of Reyes' throwing error -- to pad the Yankees' lead.
Brett Gardner moved from left field to center, and Chris Young entered to replace Ellsbury in left field, batting first.
"I think [it's] a distinct possibility [that he may not return this season]," said Girardi. "Any time a guy comes out and grabs his hamstring, you're always concerned. It's not what you want. We just lost [Martin] Prado and Jake swung the bat really well tonight. He's been a huge part of our offense. It's not what you want, but you've got to deal with it. That's all we can do."
Ellsbury has never replicated his career season in 2011, when he slugged 32 home runs and drove in 105 while staying healthy for its duration. But in 2014 he has resembled shades of that season, stealing the same amount of bases (39) and homering 16 times, more than the last two years combined, offering at least some promise for the next six years of his contract.
Still, even with the Yankees' chances at the postseason unlikely, it stung to lose arguably the team's best player this season without knowing the severity of the injury.
"You could hit Ells anywhere and he's going to be productive," said Girardi. "That's the type of player he is. He's got great speed. He's really a smart baserunner. He knows how to steal bases. He knows how to get himself into scoring position. He's a great player -- offensively, defensively, there's nothing that this kid can't do. He's meant a whole lot to our club."
Jake Kring-Schreifels is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.