SAN DIEGO - Three days after pitching 10 shutout innings, Cliff Lee was placed on the 15-day disabled list Saturday with a left oblique strain. The Phillies believe Lee may only miss a few starts, but his status is largely uncertain.

"With obliques, you just don't know how long they're going to take," Phillies general manager Ruben Amaro Jr. said. "He's shown improvement. We're hopeful that he's only going to miss a couple of starts."

The Phillies now have $57.75 million in 2012 salary on the disabled list. Kyle Kendrick will take Lee's spot in the rotation Monday against Arizona. Lee is eligible to be activated May 4.

He injured himself on a pitch in the 10th inning Wednesday. Lee was the first Phillies starter to pitch into the 10th since Terry Mulholland in 1993 and the first in baseball since 2007. But Amaro does not think the long outing was the cause of the injury. Lee threw 102 pitches. In 2011, he eclipsed that number 19 times.

"It just happened," Amaro said. "He was moving through that game pretty well and efficiently. He didn't show any signs of fatigue. He was crisp in the 10th."

Lee could leave the team and return to Philadelphia for an MRI and examination by team physician Michael Ciccotti, but Amaro said that had yet to be deemed necessary. Lee did not see a doctor in San Diego, but his soreness was evident enough to merit an absence. He complained about it the next day but the severity wasn't realized until it persisted.

The general manager said the team was being cautious with Lee, who has improved daily, Amaro claimed. He has had abdominal injuries before, but those were lower in the body than the rib cage, Amaro said. During his 11-year career, Lee has been on the disabled list three times, all for abdominal injuries. Those stints totaled 137 days.

At the end of spring training in 2010, Joe Blanton suffered an oblique strain. He spent 38 days on the disabled list and missed 24 games then. Whether Lee's ailment is as serious remains to be seen.

Kendrick threw a bullpen session Saturday and will slide into the rotation. He made 15 starts in 2011 and last pitched Tuesday. It is unknown how deep into the game Kendrick could go.

If the Phillies need another starter, Amaro said there are various options in triple-A Lehigh Valley and it would depend on how the rotation lined up. Dave Bush, Scott Elarton and Pat Misch are among the veteran pitching depth with the IronPigs.

To fill Lee's spot on the roster, the Phillies recalled lefthanded reliever Joe Savery. He will be in San Diego by first pitch on Sunday.

Contact Matt Gelb at mgelb@phillynews.com or follow on Twitter @magelb.