The 27-year-old Thompson leads the Cubs in wins with a 9-5 record and has a 3.97 ERA in 25 games. He has made 17 starts since joining Chicago's rotation May 11.
Manager David Ross doesn't believe Thompson's injury is serious, but said it affected the righty Friday against Milwaukee when he allowed five runs -- all from home runs -- in 3⅔ innings in a second straight shaky start.
"Is it something we're super long-term concerned about? No," Ross said Saturday before the rain-delayed game against the Brewers. "It makes a lot of sense to make sure we take care of this, this doesn't pop up to be something major."
Thompson has pitched 104⅓ innings this season, the most for him since 2018 in the minors. He's in his second year in the majors.
Espinoza was recalled from the minors for the sixth time this season. He is 0-2 with a 4.11 ERA in six games with the Cubs in 2022.