He had allowed two earned runs in seven innings to the San Diego Padres, surely a good night for Joe Blanton. But the pitcher was not exactly pleased.

"I didn't feel like I had my best stuff," Blanton said Saturday after the Phillies' 4-2 win.

Five days later, the cause for that uneasy feeling was realized. Blanton was placed on the 15-day disabled list Thursday with a medial impingement in his right elbow. The move is retroactive to April 24, meaning Blanton can be activated May 9.

Phillies general manager Ruben Amaro Jr. said an MRI exam on Blanton's elbow on Thursday was encouraging because there was no structural damage evident. But Blanton has felt the discomfort for a few starts, and Amaro said it was best for the team to shut him down. There is no timetable on a return for Blanton, but Amaro does not expect it to be a prolonged absence.

"We just don't know," Amaro said. "It'll be a shorter one. We'll find out. We're generally pleased with the MRI."

Elbow impingements sometimes require surgery but are usually cured by rest and nonoperative treatment. An impingement occurs when a thin layer of membrane that lines the elbow becomes caught in the elbow joint.

Meanwhile, catcher Carlos Ruiz will not need to go on the disabled list with soreness in his lower back, Amaro said. An MRI exam showed no issues, but Ruiz is still feeling some discomfort, Amaro said, which could lead to the team adding a third catcher for a few days. Starter Roy Oswalt remains with his family in tornado-ravaged Mississippi, and Amaro said he was still unsure if the righthander will be back for his next scheduled start Tuesday.

To replace Blanton, the Phillies called up righthander Vance Worley from triple-A Lehigh Valley. He will assume Blanton's spot in the rotation, which means he starts Friday night in the series opener against the New York Mets at Citizens Bank Park.

The Phillies could have opted for Kyle Kendrick, who last pitched Tuesday, throwing 21 pitches in two innings. But Amaro said that would be a disservice to both team and pitcher because Kendrick has done adequately in his current relief role.

Instead, Worley, who burst onto the Phillies radar in 2010, will make his first appearance in the majors this season. Worley, 23, last started Sunday for the IronPigs, so he will be on his regular turn. He is also stretched out as a starter, while Kendrick is not.

In four starts at triple A, Worley had a 2.78 ERA. In 222/3 innings, he struck out 25 and walked just six. Worley pitched in five major-league games in 2010 and had a 1.38 ERA with a 12-4 strikeout-to-walk ratio.

The proof of Blanton's discomfort comes in his velocity readings from his last start. Against San Diego, Blanton's sinker had an average speed of 87.5 m.p.h., according to Pitch F/X data. In his first three starts, his average sinker velocity was 89.3 m.p.h. Last season, he threw his sinker at an average speed of 89.4 m.p.h.

Blanton has a 5.92 ERA in four starts.

"It wasn't as crisp," Blanton said Saturday when pressed about his dissatisfaction. "It wasn't bad. I threw a lot of balls out of the gate. I tightened it up a little bit. I felt good about the way I finished."

Blanton is the seventh member of the Phillies' 40-man roster to be placed on the disabled list, joining Brian Bocock, Domonic Brown, Jose Contreras, Brad Lidge, J.C. Romero, and Chase Utley.

If the Phillies need an extra catcher for a few days with Ruiz down, they would opt for either Erik Kratz or Dane Sardinha. Kratz has been the hotter hitter of late.

As for Oswalt, the Phillies have some flexibility with another off day on Monday. If he is not ready to return for his next scheduled start Tuesday, the team could skip him in the rotation.

But with Worley already inserted for Blanton and a bunch of starters who have sustained high pitch counts in April, that is something the Phillies likely want to avoid.