Relievers Liam Hendriks of the Chicago White Sox, Jordan Romano of Toronto and Devin Williams of Milwaukee replaced them on the active rosters for Tuesday's game at Dodger Stadium, Major League Baseball said Sunday.
Mikolas gets a $50,000 bonus for his selection, Hendriks $15,000 and Romano $10,000.
About one-fifth of the rosters have changed since the original 33-man teams were announced on July 6 and 8.
Los Angeles Dodgers left-hander Tyler Anderson and the San Francisco Giants' Carlos Rodon were among previous pitching additions. After being added, Rodon was then dropped because of a cracked nail and blister on the middle finger of his pitching hand.
Milwaukee closer Josh Hader was among the pitchers who previously dropped out.
The Associated Press contributed to this report.