Plesac went out with friends Saturday in Chicago, which angered teammates and club officials.
The 25-year-old will be isolated for 72 hours and tested daily as the club attempts to avoid a breakout similar to those faced by the Miami Marlins and St. Louis Cardinals, which have led to multiple game postponements. The Indians could choose to take further preventative measures, Rosenthal and Meisel add.
"I would like to apologize to my teammates, the entire Cleveland organization and all of our fans for my actions Saturday evening," Plesac said in a statement that Mandy Bell of MLB.com obtained. "I realize I made a poor choice to leave the hotel, which broke protocols and could have endangered other people.
"I understand that in these times of uncertainty, I need to be more vigilant and responsible and I'm determined to earn my teammates' forgiveness and get back to work."
"We love Zach," Indians ace Shane Bieber said following Sunday's victory against the Chicago White Sox, according to Jon Morosi of MLB Network. "We support him. But he screwed up ... We're going to handle this in-house. We need to focus on one thing at a time, and that was the game. I'm proud of the guys for being able to handle one thing at a time."
Plesac has authored a 1.29 ERA and 2.20 FIP in 21 innings over three starts.