Mets general manager Sandy Alderson would not give details about Harvey's infraction, saying that he was sent home and that his suspension started Saturday.
"We'll keep it in-house, the way it's supposed to be," manager Terry Collins said before Sunday’s game.
Left-hander Adam Wilk was called up from Triple-A to replace Harvey as the Mets' starter Sunday against the Marlins, ESPN reported. Noah Syndergaard was placed on the 60-day disabled list to make room for Wilk on the 40-man roster, the New York Daily News reported.
Collins said the suspension was a tough decision.
"There's things with this job that certainly are internal that the public can't see, and how hard it is, and this one's a tough one," Collins told the Daily News. "So we hope to put it behind us and move forward.
The Mets were involved in another controversy Saturday when a photo posted by the team on social media unwittingly showed a sex toy that was in Kevin Plawecki’s locker, the Daily News reported. An MLB source told ESPN on Sunday that Harvey's suspension had nothing to do with that incident. Plawecki has said he had no knowledge of the toy being in his locker.
Harvey, 28, is 2-2 with a 5.14 ERA in six starts this year as he tries to rebound from the surgery for thoracic outlet syndrome that ended his 2016 season. The right-hander made 17 starts last season, going 4-10 with a 4.86 ERA.
Harvey's best season was in 2015, when he went 13-8 with a 2.71 ERA and led the Mets to the World Series.