CHICAGO -- The Boston Red Sox got good news for their rotation Tuesday night, when left-hander Eduardo Rodriguez turned in a solid outing at Triple-A Pawtucket in his latest rehab start.

Rodriguez, 23, threw six innings and allowed three runs, all in the first inning, and struck out three. He finished especially strong, retiring 16 of the last 18 batters he faced.

Red Sox manager John Farrell said Wednesday that he was pleased with the outcome and revealed what's next for Rodriguez.

"He'll make his next start with Pawtucket on Sunday [May 8], with upwards of 90 to 100 pitches the next time out, and hopefully to make the same strides he made between the first and second starts on rehab," Farrell said. "From the second to the sixth innings, they were probably more crisp, more sharp. We're looking for that to continue, to advance."

A third rehab outing at Pawtucket on May 8 would put Rodriguez in line for a start on May 13 at Fenway Park against the Houston Astros, but Farrell declined to project that as a possibility.

"It's probably a little bit too early to tell," Farrell said. "I think with each outing he's gaining more confidence and feeling more natural and free on the mound. We'll assess after he gets through Sunday's game."

Rodriguez's return is highly anticipated because of his performance as a big league rookie with the Red Sox last season. Flashing a 95 mph four-seam fastball to mix in with a strong slider and changeup, he posted a 10-6 record with a 3.85 ERA in 21 starts, with 98 strikeouts and 37 walks in 121⅔ innings pitched. He also logged 13 quality starts in his 21 turns.

With right-hander Joe Kelly also on the disabled list, the Red Sox rotation has had to rely upon knuckleballer Steven Wright and lefty Henry Owens.

With five straight quality starts, Wright's performance has been strong enough to merit his retention in the rotation.

Rodriguez might slide in easily enough for Owens, but Kelly's timetable for recovery should expand Boston's options later in May. After throwing a bullpen session Tuesday, Kelly is expected to head for Pawtucket to begin a rehabilitation assignment with a Friday start.

Deciding who gets forced out of the rotation in that situation would be further complicated by Wright being out of minor league options and by veteran Clay Buchholz's recent struggles. Entering Wednesday, Buchholz was 0-3 with a 6.51 ERA through his first five starts.