San Francisco, CA -- (Sports Network) - San Francisco starter Randy Johnson had to cut his outing against Houston short on Sunday after injuring his left shoulder.

The injury appeared to come in the third inning on an awkward wave at a third- strike curveball from Astros starter Roy Oswalt. He immediately reached for his shoulder but remained in the game. In the fourth, he yielded three of his four runs allowed and committed a throwing error before leaving. The initial diagnosis is a strain.

"Very scary. I thought he did something to (his left shoulder) and started throwing a lot slower than he usually throws...89-91 and all of the sudden you see this guy throwing 82. You just hope and pray that nothing happens to him seriously and that he's okay for the next start," said battery mate Bengie Molina.

Johnson was attempting to win a third consecutive start and fourth straight decision but took the loss in lasting just 3 2/3 frames. The five-time Cy Young Award winner, who picked up career win No. 300 earlier this year, is now 8-6 on the season with a 4.81 earned run average through 17 starts.

The Astros went on to post a 7-1 victory.