Stephen Strasburg has strained forearm

WASHINGTON -- Stephen Strasburg is headed back to the disabled list, and his prized right arm will undergo yet another examination that will largely determine whether he pitches again this season.

The Washington Nationals rookie will have a second MRI exam to see if anything more than a strained tendon in his forearm caused him to grimace after throwing a changeup in Saturday's game at Philadelphia. Strasburg was removed from the game and underwent an MRI on Sunday.

The MRI "showed some things on there that led us to set up another MRI," general manager Mike Rizzo said Monday. The GM said the upcoming test will be done in the "next day or two" and will use an injection of dye that should render "a full view of what's going on in there."

For now, the Nationals are still calling Strasburg's injury a flexor strain in his throwing arm. He had been scheduled to start again Thursday, but instead will find himself on the disabled list for the second time in less than a month. The Nationals are expected to soon make the move official.

"He's anxious to find out what's going on," Rizzo said. "He felt good today. His elbow felt good. ... To say he's little anxious, a little emotional would be fair to say."

Strasburg, who is 5-3 with a 2.91 ERA and 92 strikeouts in 68 innings, was hurt while making his third start since returning from the disabled list because of inflammation in the back of his right shoulder.

Rizzo said Strasburg arrived at Nationals Park on Monday hoping to do some throwing. The Nationals, who have been extremely cautious with Strasburg's development, told him no. Strasburg has told the team he had a similar problem in college at San Diego State and pitched through it. He was the overall No. 1 pick in the 2009 draft.

"It's discouraging for Stephen," manager Jim Riggleman said.

The Nationals clarified remarks Rizzo made Sunday, when the general manager said Strasburg went through a normal post-start workout that including some light throwing. The Nationals said Rizzo misspoke and that Strasburg did not throw on Sunday.

Rizzo wouldn't speculate on whether Strasburg could be shelved for the season, saying the team will wait for the results on the next test and take a "prudent course of action after that." Fellow Nationals starter John Lannan also had swelling around his flexor tendon earlier this season and missed one start.

The Nationals have been careful to limit the innings and take every other precaution with their 22-year-old phenom -- he was taken out of a game recently because of a protest in the outfield that delayed the game for a few minutes.

Riggleman is familiar with promising pitchers who flame out early, having managed a young Kerry Wood with the Chicago Cubs. Riggleman said it's important to properly deal with the "red flags" that arise early.

"It just seems like pitchers get to a point where they're past all the issues, guys like Livan [Hernandez] and Miguel [Batista]," Riggleman said. "It just seems like it's the way it goes with these young pitchers."