KANSAS CITY -- This was shaping up as the season that highly-touted Red Sox prospect Ryan Lavarnway would get his September callup.

But that time-table was pushed up Thursday, when Kevin Youkilis was placed on the 15-day disabled list with a back injury. The Red Sox are also without David Ortiz (right heel bursitis) for a few more days. That will give Lavarnway -- a catcher by trade -- the chance to serve as the designated hitter during Big Papi's absence.

Lavarnway has 30 homers between Double-A Portland and Triple-A Pawtucket this year, batting .293 overall. He's hit .301 in 55 games with the PawSox, though he's gone just 5-for-44 in August. Three of the five hits were home runs.

He had typical nerves entering his debut Thursday, when he batted seventh in manager Terry Francona's lineup.

"It was pretty bad on the plane, I had some knots in my stomach," said Lavarnway. "Now that I'm here, it's kind of back to business."

The Red Sox felt that Lavarnway was already pretty close to being a Major League-caliber hitter, if he isn't one already. The key to his development is working on his defense behind the plate. During this stint in Boston, he would only catch during an emergency situation, as Francona already has a solid tandem of Jarrod Saltalamacchia and Jason Varitek.

"We have catching, but we can hopefully use his bat," Francona said. "He's a tremendous hitter -- especially for power. He started out in Double-A, carried it over to Triple-A. He's worked so hard on his catching -- he's kind of actually probably turned into an average catcher, because that's where he had some work to do. Now you might not see him catch while he's here, but he'll hopefully hit a few home runs."

Lavarnway, an eighth-round selection by the Red Sox in the 2008 First-Year Player Draft, was keeping an even keel as he got ready for the game.

"I don't have a lot of expectations coming in," said Lavarnway, who went 0-for-4 in his debut. "I'm just coming in with an open mind and trying to learn something every day."

Crawford once again struggling with mechanics

KANSAS CITY -- Left fielder Carl Crawford, who has shown glimpses of the All-Star player he was with the Rays, entered this four-game series in Kansas City mired in another slump.

Crawford went 0-for-9 in the three-game series against Tampa Bay, and he has four hits in his last 31 at-bats.

"The last week has been tough," said manager Terry Francona. "He's a little bit late again on his setup. When he gets back to close, he's a little bit late, so he's rushing. He's just not getting the pitches that he has. He knows it, we know it. Sometimes saying it and doing it are a little harder to do."

It looked like Crawford was ready to bust out during the three-game series against the Yankees from Aug. 5-7, going 9-for-12.

"You would think," Crawford said. "Unfortunately, it hasn't [clicked] and you just have to keep playing."

Crawford, who batted sixth on Thursday, is hitting .249 with seven homers and 38 RBIs.

Scutaro out of lineup again, but getting closer

KANSAS CITY -- For the fifth straight game, Marco Scutaro was out of the Red Sox's lineup with back spasms. However, he appears to be getting close to a return.

"I hope a little bit better," said manager Terry Francona. "He called [trainer Mike Reinold] today and said he was starting to feel a little bit better, so we'll see how he does."

Scutaro noticed his back was starting to improve on Tuesday. He was hoping to go through a normal pregame routine on Thursday.

With Kevin Youkilis on the 15-day disabled list, Mike Aviles played short, with Jed Lowrie at third.

For Aviles, it was a return engagement to Kansas City, the team that traded him to the Red Sox on July 30.