Pitching for Double-A Springfield, Mulder gave up three runs on two hits and three walks in the first inning before finding his rhythm. He allowed six hits overall, including a home run, with four walks and five strikeouts.
The left-hander is expected to make at least a few more rehab starts before rejoining the rotation. He threw six scoreless innings in his last outing, also for Springfield.
Mulder has been limited to 20 major league starts the last two seasons due to shoulder woes. He made only three starts last year, going 0-3 with a 12.27 ERA, before undergoing a second shoulder operation in September.
