KANSAS CITY, Mo. -- The Boston Red Sox placed third baseman Kevin Youkilis on the disabled list because of a back injury Thursday and called up catching prospect Ryan Lavarnway from Triple-A Pawtucket.
Red Sox manager Terry Francona announced the moves before the opener of a four-game series against the Kansas City Royals, which the Red Sox won, 4-3. The 24-year-old Lavarnway made his major league debut as the designated hitter, batting seventh in the Red Sox lineup. He went 0-for-4.
Youkilis, who is hitting .266 with 17 homers and 78 RBIs, has missed several games recently because of what Francona called "a back strain or sprain." Youkilis remained in Boston after Wednesday night's game against Tampa Bay to be examined by doctors at Massachusetts General Hospital. He also received an injection to alleviate some of the pain in his lower back.
"His body was so beat up anyway, I think this was the last straw, kind of put him over the edge," Francona said. "But hopefully we can get him back to where he can be Youkilis. I think after the game yesterday, it was obvious we needed to get him checked out."
The 32-year-old Youkilis was selected to his third All-Star Game this summer. He joins a rapidly growing Boston disabled list that includes designated hitter David Ortiz (bursitis in right foot), reliever Bobby Jenks (sore back), and outfielder J.D. Drew (left shoulder impingement).
"You lose one, it's kind of a big deal, you lose two it doesn't help," Francona said. "But you know, our challenge is to not let it affect us winning games, so that's what we'll do."
Francona also indicated that Marco Scutaro, who is out with a stiff back, is getting closer to returning. He hasn't played since Aug. 13.
Aviles played shortstop on Thursday, while Lowrie played third.
Lavarnway could have the opportunity to catch, though his defense has not progressed nearly as rapidly as his bat. He was hitting a combined .293 with 30 homers and 85 RBIs at Double-A and Triple-A, and that's why Francona expects him to be primarily the designated hitter while he's with the team.
"I tried to keep my head out of the roster up here," said Lavarnway, a sixth-round draft pick in 2008 who has shown considerable power at every level. "I didn't want to get too ahead of myself."
Lavarnway said he didn't expect to make it to the majors so quickly, and he hardly worked with the starting pitchers in spring training, when young catchers who might have a chance of making the major league team are usually given a look. He flew into Kansas City on Thursday morning, but still wasn't entirely sure he was added to the roster until he landed in the afternoon.
"It was bad on the plane. I had knots in my stomach," he said. "Now that I'm here, it's back to business. The routine of the day will help me get back into it."
To make room on the 40-man roster for Lavarnway, the Red Sox designated left-hander Randy Williams for assignment.
In other news, Andrew Miller will return to the starting rotation for the Red Sox on Friday for the first time in two weeks. He'll also be returning to Kauffman Stadium, where he has had two opposite experiences in his only two appearances.
In 2006, Miller recorded the final out to clinch the Detroit Tigers' first playoff berth since 1987.
In his only other appearance in Kansas City, a start in 2007, Miller recorded only two outs and gave up five hits and five runs in a loss.
He's 4-1 with a 5.40 ERA this season with the Red Sox.
Information from ESPNBoston.com freelancer Jayson Jenks and The Associated Press was used in this report.