BOSTON -- Red Sox right-hander Michael Wacha was scratched from his scheduled start in Sunday's series finale against the White Sox and was placed on the 15-day injured list.
Manager Alex Cora said Wacha was feeling sore on his left side after his last bullpen session.
"[Saturday] we had an MRI and everything was clean," Cora said. "We're just going to be smart about it. Hopefully, he can continue to progress, get on the mound and be ready for [his next start]."
About an hour after Cora's media session, the Red Sox put Wacha on the injured list with what was described as "left intercostal irritation." Right-hander Tyler Danish was recalled from Triple-A Worcester to fill his roster spot.
Wacha (3-0, 1.38 ERA), 30, signed a one-year, $7 million deal during spring training. He has been one of the team's best starters, allowing two or fewer runs and going five-plus innings in each of his last four starts.
Right-hander Tanner Houck (2-3) took his place against Chicago and allowed four hits and three earned runs in 2⅔ innings pitched, taking the loss as Boston fell 3-2.
Last-place Boston (10-19) has lost five straight and 14 of 18.
The Associated Press contributed to this report.