NEW YORK -- The Yankees put first baseman Garrett Cooper on the 10-day disabled list Thursday with tendinitis in his left hamstring and promoted Tyler Austin from Triple-A Scranton/Wilkes-Barre.
Austin was in the lineup at first base and batting seventh as New York tried for a four-game sweep of its Subway Series against the crosstown-rival Mets. Chase Headley was given a rest.
With projected regular Greg Bird sidelined by an ankle injury most of the year, the Yankees have started nine players at first base this season.
Cooper was acquired in a trade with Milwaukee on July 13 to help shore up the position. He is batting .326 with six RBIs in 13 games for New York.
Yankees manager Joe Girardi said Cooper told the team his hamstring was bothering him after his first at-bat Wednesday night, when he lunged for the bag as he tried to beat out an RBI groundout.
He had an MRI that "came back pretty good," Girardi said.
"He's had some hamstring issues before," the manager added. "We don't think it'll be a long stint, but we figured we'd better DL him."
Austin, who homered in his first major league at-bat last August, started this season on the DL with a broken left ankle. He also missed six weeks with a strained right hamstring and was 2 for 13 (.154) with a home run and two RBIs in four major league games this season.
Including rehab assignments, Austin has batted .304 with seven homers and 28 RBIs in 44 combined games at Double-A and Triple-A this year. The righty hitter will play first base against some left-handers, Girardi said.
The second-place Yankees were set to face struggling Mets lefty Steven Matz on Thursday night and at least two more lefties this weekend during a pivotal series at AL East-leading Boston.
"We're looking for some big at-bats," Girardi said.
Bird began another rehab assignment Wednesday night at Triple-A. He will be joined by All-Star second baseman Starlin Castro (strained right hamstring) on Friday, the same day designated hitter Matt Holliday (back) reports to Class A Tampa to start playing rehab games.
Girardi said closer Aroldis Chapman probably would be unavailable for the second consecutive night. Chapman's hamstring tightened up as he saved Tuesday's win over the Mets.
"I think we're going to have him throw a little bit more today and see how he feels," Girardi said.
New York began the night 4½ games behind idle Boston.