The Nationals announced the decision Tuesday, saying it was retroactive to Saturday. In corresponding roster moves, the team selected the contract of right-hander Justin Miller from Triple-A Rochester and designated right-hander Rogelio Armenteros for assignment.
Scherzer "tweaked" his groin in the first inning during his start against the San Francisco Giants on Friday. On Monday, he had a bullpen session, which was expected to be about 31 pitches. Scherzer, however, only threw 10 pitches before stopping due to the groin ailment.
The 36-year-old Scherzer was scheduled to pitch Wednesday in the finale of a three-game series against the Pittsburgh Pirates. Washington initially considered pushing his start back, but the team ultimately decided to put him on the IL.
"I just want to be more cautious than not," Nationals manager Dave Martinez said. "This is an injury that, right now, it's getting better. So we want it to completely get better.
"It's something that we don't want him to reinjure with the fact that we're going to force him to try to pitch. So we'll give him a few extra days, and hopefully it won't take long for him to come back and he'll just miss a start."
Scherzer, a three-time Cy Young Award winner, has a 5-4 record and 2.21 ERA with 104 strikeouts over 13 starts this season.