Before Saturday's game, the Nationals announced that Olsen was going to miss his scheduled start Thursday in San Francisco because of inflammation in his pitching shoulder. Olsen was removed from Friday's game against Baltimore after only three innings and underwent an MRI exam that showed no structural damage to his surgically repaired shoulder.
Following a 7-6 loss to the Orioles, Washington announced Olsen was going on the disabled list instead.
"At this point, the training staff doesn't want him to play catch for about five days," Washington manager Jim Riggleman said. "By the time he throws a good bullpen session or two, it's turning into two starts."
The 26-year-old Olsen is 2-2 with a 3.77 ERA in eight starts.
A corresponding move will be made before the Nationals conclude their interleague series against the Orioles on Sunday.
Because of an off day Monday, Riggleman said the rest of the rotation would stay on turn. He did not know who would start next Saturday in San Diego.
Rodriguez, who is hitting .325 with a homer and 16 RBIs, left Saturday's game with lower back tightness.
He appeared to hurt himself on a third-inning swing, but remained in the game and grounded out. Rodriguez was replaced by Wil Nieves in the top of the fourth.
"When you squat that many years, sometimes you get tight in the lower back," Rodriguez said. "I'll be fine in a few days."
The 38-year-old Rodriguez, who was scheduled to get Sunday off, hopes to play sometime during Washington's midweek series in San Francisco.