Buck, scratched before Wednesday's game after straining his right oblique during batting practice, was placed on the 15-day DL alongside second baseman Mark Ellis. To make room for Buck, the A's recalled outfielder Matt Carson from Triple-A Sacramento.
The 26-year-old Buck was somewhat-of-a surprise roster choice heading into the season, but Coco Crisp's fractured pinkie finger opened a rather-wide door for Buck. It marked the third straight season Buck has made the A's Opening Day roster, but four previous stints on the disabled list and options to Sacramento in each of the last two years limited him to just 156 games over those three seasons.
Buck was batting .219, but was 3-for-9 on the homestand and hit a solo homer -- his first of the year -- in Tuesday's 7-3 loss to the Yankees before becoming the eighth Oakland player to join the DL this season.
"He was right there and looking good," manager Bob Geren said. "When you're just starting to look real good, it magnifies it."
Meanwhile, the 28-year-old Carson was swinging a hot bat in Sacramento, where he was hitting .357 with six RBIs in 14 games for the River Cats. In 10 contests as a September callup with the A's last year, he went 6-for-21.
"He was hitting the ball extremely well in Triple-A," Geren said. "It's nice to have someone come up who's doing so well. He's a fundamentally sound outfielder who has some power and uses the whole field. It's nice to have someone of his caliber."
The A's skipper wasted no time in getting Carson work, placing him in the starting lineup in left field against the visiting Yankees on Thursday.
"I'm feeling more relaxed, more comfortable," Carson said. "Last year I pressed a little bit."
In order to clear space for Carson on the 40-man roster, the A's designated outfielder Jai Miller -- claimed off waivers from the Marlins on April 8 -- for assignment.
Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.