Ausmus declined to elaborate on the move, though the decision appears to have come after a bizarre appearance in Monday's game in which Rondon's fastball velocity was markedly lower than usual.
Ausmus said after Game 2 of Monday's doubleheader against the Chicago White Sox that Rondon was not injured. Asked earlier in the week if Rondon was trying to dial back his velocity to improve command, Ausmus said the team had previously advised against this approach.
Ausmus declined to elaborate further on the decision, shutting down questions about the nature or the timing of the move.
"Other than saying that [general manager] Al Avila and myself completely agreed on it, there will be no other details or comment," Ausmus said Tuesday.
Avila echoed a similar message.
"Brad and I met and we agreed that the course of action was best for Bruce and the club," Avila told ESPN via text message Tuesday afternoon.
The team learned about the decision before Ausmus' announcement. The news is another significant blow for the Tigers, who have experienced pitching woes all season.
When asked about the team losing a "big component" of its pitching staff, veteran catcher Alex Avila responded that "to be a big component of the team, you've got to be here."
"You put out your best effort every day, no matter the situation," the Tigers catcher said.
Rondon's departure leaves the Tigers without a clearly defined closer for the immediate future -- although Neftali Feliz and Alex Wilson appear to be the leading candidates -- and it further clouds the team's long-term needs at the position if effort continues to be an issue for the 24-year-old, who was groomed to take on the role.
Rondon was moved into the closing role in August, with Wilson suffering from shoulder fatigue, and his audition has yielded mixed reviews.
Although he has a powerful arm with strong fastball velocity, Rondon has struggled at times to locate his pitches. Additionally, he has seen his velocity decline over the past week, which has prompted questions. According to the Comerica Park radar guns, his velocity on Monday was in the low-to-mid 90s, whereas previously it had been upwards of 97-100.
Ausmus said after the game that he was not sure why Rondon's velocity had dropped but also said the team consulted with the right-hander to see whether he was injured. Rondon said he was fine.
At least some people -- including a few scouts that were on hand for Monday's game -- believe Rondon was dialing it back intentionally. Exactly why he was doing that is not immediately clear.
Talking about the situation on the team's Tuesday night broadcast, radio announcer Jim Price was outspoken about Rondon's actions.
"What he did is unforgiveable," Price said.
ESPN MLB analyst Eduardo Perez called Rondon an "embarrassment to the game of baseball" and suggested this course of action to the Tigers: "Trade him."
Rondon declined to speak to reporters after Monday's game, in which he retired all three batters faced in the ninth inning.
Ausmus was asked earlier Monday which player had the most power to influence or affect next season with his play in 2016. Ausmus did not hesitate, replying, "Bruce Rondon."