Clayton Kershaw only starts about 20 percent of the Dodgers’ games, so you hate to see them spoiled.

But on a night that Kershaw pitched his fourth complete game of the season and Matt Kemp had a double and triple in a 6-2 victory over San Diego, the Dodgers took what I would consider to be their worst blow of the season, non-ownership division, as well as their first big blow of 2012.

Rubby De La Rosa, the prized rookie who figured to be a significant cog of the 2012 Dodger starting rotation, has a sprained ligament in his right elbow and will miss considerable time, with surgery a distinct possibility. Here’s Tony Jackson of

… De La Rosa faces the possibility of season-ending elbow surgery after an MRI exam on Monday revealed a sprained ulnar-collateral ligament. A team spokesman said De La Rosa and the medical staff presently are considering a handful of treatment options, one of which would be surgery.

Even if De La Rosa were to decide against surgery, he could be done for the year. The Dodgers have only 54 games remaining, and De La Rosa’s innings were being closely monitored anyway because he is considered such an important part of the franchise’s future. Between the minors and majors, he has pitched 100 2/3 so far this season. …

Dodgers medical-services director Stan Conte said De La Rosa reported tightness in his elbow immediately after leaving the game, but that he initially had felt it while throwing a pitch in the third inning. De La Rosa saw team physician Dr. Neal ElAttrache, who recommended he undergo an MRI exam.

Conte said the decision to put De La Rosa on the DL so quickly came because he likely would have missed his next start anyway. Mattingly said Ely initially will pitch out of the bullpen and that with an off-day on Thursday and De La Rosa’s rotation spot not due to come up again until Saturday night at Arizona, the Dodgers might simply skip that spot. That would mean they wouldn’t need a fifth starter again until Aug. 9 against the Philadelphia Phillies.

Aside from losing the treat of seeing De La Rosa pitch, what this may well mean is that more of the money that is needed to rebuild the Dodger offense in the offseason might now have to be reallocated to pitching.

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Alex Castellanos went 0 for 4 with a walk in his debut in the Dodger organization, in a 6-4 Chattanooga victory. Juan Rodriguez pitched two shutout innings for Great Lakes in a 9-2 win.