CINCINNATI -- An already depleted Reds rotation will have to plow ahead while another starting pitcher is on the injured list.
On Thursday, Brandon Williamson went on the 15-day IL with left shoulder fatigue.
Williamson, who pitched only three innings and allowed four runs with four hits and four walks during Wednesday's 13-2 loss to the Rockies before exiting, underwent an MRI on Thursday morning.
“Structurally, it came back good, so that’s good," manager Terry Francona said. “Dr. [Tim] Kremchek looked at him, injected his shoulder with cortisone and he will go on a shoulder program -- range of motion, strength and all that stuff.”
There was no timeline for Williamson's return that was immediately known, but because the left-hander has had a history of shoulder issues, there will need to be extra caution.
The most serious problem was when a left shoulder strain in 2024 put Williamson on the IL for five months. Four games into his return, he tore the ulnar collateral ligament in his left elbow and needed Tommy John surgery that cost him all of 2025.
Cincinnati is already without starting pitchers Hunter Greene (right elbow) and Nick Lodolo (left index finger blister), which enabled Chase Burns, Rhett Lowder and Williamson to all make the big league rotation out of camp at Spring Training.
Williamson, who arguably had the best spring of any Reds starter, is 2-3 with a 6.11 ERA in six starts.
Reliever Zach Maxwell (Cincinnati's No. 17 prospect) was recalled from Triple-A Louisville to fill the roster spot, but the Reds will need a starter to take Williamson's next turn on Monday vs. the Cubs at Wrigley Field.
Francona and the club are still determining who might get that turn.
“We’ve got to see how we get there and stuff like that. We’ve got a lot of moving parts," Francona said.
Lodolo is not a candidate for the start because he is scheduled to make a rehab assignment start for Louisville at Omaha on Saturday as he continues to build up. Jose Franco, who was recalled on Saturday to fill a bullpen spot, is a starter and could be an option.
At Louisville, Chase Petty (Reds' No. 7 prospect) pitched for Louisville at Omaha on Wednesday and would be able to pitch Monday on normal rest if he was called up. Petty pitched just 2 1/3 innings in that start, but he also made 62 pitches in that short period.
Another prospect, Julian Aguiar (No. 18), has been on the IL for Louisville with a right elbow valgus extension overload since last pitching on April 8. Aguiar also missed 2025 rehabbing from Tommy John surgery.