San Francisco, CA -- (Sports Network) - San Francisco starter Randy Johnson was forced onto the 15-day disabled list one day after having to exit Sunday's start against Houston after straining 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.

Battery mate Bengie Molina noted after the game that Johnson's velocity dipped after the swing. He 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.

To fill the roster spot, San Francisco recalled infielder Kevin Frandsen from Triple-A Fresno. This will mark his third stint with the parent club having batted 0.71 (2-for-28) in nine games this year. He has a .304 average with eight home runs and 33 runs batted in over 64 games with Fresno.