Giants starter Randy Johnson was scheduled to undergo an MRI on his strained left shoulder on Monday. Johnson left his start against the Astros on Sunday with the injury. "It's a strain, I'm getting an MRI. That's all I have to say," the lefty said after the game. Johnson's velocity dipped drastically after he swung awkwardly at the plate in the bottom of the third inning. He left the game in the top of the fourth. "It was very scary," catcher Bengie Molina said. "He usually throws 89, 90, 91 (mph), and all of the sudden you see this guy throwing 82. We just hope and pray nothing happened to him seriously and he's OK for his next start."