"Though the Giants maintained a 11/2-game lead in the wild-card race after their 7-1 loss to Houston on Sunday afternoon, their potential run to the postseason might have taken a disheartening turn.

Randy Johnson left the game in the fourth, an inning after injuring his throwing shoulder on an off-balanced swing. The Giants are calling it a "shoulder strain" and waiting for MRI test results today before making predictions about the severity.

"It was very scary," Bengie Molina said. "He was throwing a lot slower. You just hope and pray that nothing happened too serious and he can make his next start."

The images of Johnson laboring in pain were about as frightening as his postgame chat with the media was brief. "Let's just keep it short: It's a strain right now, and I'm getting an MRI. That's all I'm saying," Johnson said.

Johnson reached for his shoulder before he even finished an awkward swing against Roy Oswalt - who subdued the Giants' bats and a crowd of 30,157. Saying he had returned to the mound after feeling a similar twinge in his shoulder in the past, Johnson threw 20 pitches in the fourth - none faster than 83 mph - and gave up two solo homers.

He recoiled in pain after an errant, sidearm throw to first on an Oswalt comebacker - allowing Jeff Keppinger to score from first to make it 4-0. Johnson called for the trainer after tossing a 79 mph pitch to the next batter, Kazuo Matsui, and left the game with a grimace on his face.

Regardless of the seriousness of the injury, Johnson could miss his next start, which is scheduled for Friday, because the All-Star break begins July 13. If the Giants do skip Johnson and then move him down in the rotation after the break, he could get as many as 15 days of rest.

"If we think there is anything going on, we'll give him some extra time," manager Bruce Bochy said."