Strasburg, 27, threw a bullpen session Tuesday afternoon before Washington was set to play the New York Mets. He was scratched from his last two starts because of the back injury and was placed on the disabled list Sunday retroactive to June 16.
Manager Dusty Baker said the MRI made him feel better and that he prayed and knew Strasburg was going to be all right.
Strasburg is 10-0 with a 2.90 ERA this season. He signed a $175 million, seven-year contract extension in May.