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02/22/12 6:56 PM EST

Tight back delays Kershaw's first bullpen

GLENDALE, Ariz. -- Dodgers Cy Young winner Clayton Kershaw missed his first bullpen session of Spring Training on Wednesday as a precautionary measure due to mild back tightness.

Kershaw, who signed a two-year, $19 million contract earlier this month, referred questions to the club's athletic training department. A team spokesman said Kershaw felt a tight muscle in the middle of his back during workouts before reporting earlier this week.

Wednesday was the first workout at Camelback Ranch-Glendale for pitchers and catchers, and Kershaw was originally in the first day's group to throw bullpen sessions. He did play catch and worked out at the various stations. He is not expected to throw a bullpen session before Friday.

While winning the pitcher's Triple Crown last year (wins, ERA and strikeouts), Kershaw also finished third in the league with a career-high 233 1/3 innings pitched. He turns 24 next month. During his first two seasons in the Major Leagues, manager Joe Torre tried to limit his pitches to 100 per start to protect his arm.

Speaking about Kershaw before Wednesday's workout, manager Don Mattingly had this to say about his ace's Spring Training routine:

"He's been around for a while, we know he's young and he's thrown a lot of innings and we won't do anything to jeopardize him."

The only injury Kershaw has suffered with the Dodgers was a separated right (non-throwing) shoulder in 2009 when he ran into an outfield fence while shagging fly balls.

Fellow left-handed starting pitcher Ted Lilly, still home after the Tuesday birth of his daughter, is expected in camp Friday.

Reliever Ronald Belisario, who had a tooth extracted Tuesday, also skipped his first bullpen session Wednesday but said he would make it Thursday. Non-roster pitcher Shane Lindsay was out with a slight latissimus dorsi strain.

De La Rosa feeling 'perfect' in elbow rehab

GLENDALE, Ariz. -- Rubby De La Rosa is a pitcher, not a doctor, but he's declared his Tommy John elbow reconstruction a success and predicts a return this season "after the All-Star break."

"It's unbelievable, perfect," said De La Rosa, whose meteoric rise to the Major Leagues last year was derailed by one bad pitch that tore his ulnar collateral ligament. "I'm going to be a lot better. No doubt I'll be 100 percent."

Dr. Frank Jobe, inventor of the operation, insists that the transplanted tendon (De La Rosa's came from his right forearm) forms a stronger joint than the original ligament.

De La Rosa, six months into recovery, said he hasn't had any setbacks and is throwing 90 feet on flat ground with a target of April to be throwing off a mound. He said he feels healthy enough to air it out, but the training staff has him reined in to throw easy.

"I have to wait," he said. "I want to be healthy. Sometimes I want to throw hard."

Except for one week home in the Dominican Republic, he spent the offseason rehabbing in Arizona. He said he's a little surprised at how well the rehab has gone, considering the stories he's heard from other patients, like current teammate Javy Guerra and former teammate Luis Vasquez.

"Sometimes it takes two years and you're not back," he said.

De La Rosa said he was injured on one pitch in an Aug. 1 game against Arizona. Earlier in the game, he was clocked five times at 99 mph. The club is undecided whether De La Rosa will return sooner as a reliever or later as a starter.

Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.