BOSTON -- Look for Nathan Eovaldi to start his stint as a reliever for the Red Sox this weekend, when the club plays a three-game series in Baltimore.

To tune up for his switch in roles, Eovaldi will pitch in a Minor League rehab game for Triple-A Pawtucket on Thursday.

The one thing that could alter the plan is rain that is expected to be in the area on Thursday. Pawtucket's game against Louisville is scheduled for 11:05 a.m. ET.

"He's going one inning," said Red Sox manager Alex Cora. "See how it goes with the weather, too, but that's the plan and then we'll see where we go after that. If everything goes well, most likely he'll join us over the weekend."

The Red Sox aren't sure at what point of Pawtucket's game Eovaldi will pitch.

"When that window comes [with the weather], just pitch," Cora said. "It's tough, because we would like him to come and do the whole thing as a reliever, but if when the game starts there's a window, well, he'll go out there and pitch."

Eovaldi's presence will be a welcome addition for a bullpen that has struggled.

One area of concern of late is that Heath Hembree, who was a force earlier in the season, hasn't been as sharp since coming off the injured list on July 5. Hembree's velocity has dipped to the low 90s, particularly in his outing Tuesday, when he gave up three runs while not recording an out. The injury Hembree had, which sidelined him for nearly a month, was a right elbow extensor strain. The Red Sox don't believe that injury is still an issue.

"He feels good actually," said Cora. "Talked to [trainer] Brad [Pearson], talked to Heath, talked to [pitching coach] Dana [LeVangie]. I know velocity is down. The one thing I always say about Heath, it's about location. Regardless if he's throwing 95, 96, 91, 92, I know velocity has been down, but if he's down in the zone, it becomes flat. He needs to leave it upstairs, and everybody knows it. That's not a secret."

Other health updates

First baseman Mitch Moreland, who is recovering from a right quad injury, again wound up doing his work at Fenway Park instead of in a rehab game for Pawtucket.

Moreland took three at-bats against lefty Brian Johnson, who was pitching a simulated game. The latest plan is for Moreland to report to Pawtucket on Friday.

Johnson has been out since June 27 due to a non-baseball-related medical matter, but he is doing much better now.

"[Johnson] threw well, 25 pitches, he faced Mitch and Sam [Travis]," said Cora. "It wasn't his arm. He's fresh, he's good. It's just the repetitions now. We'll see how he reacts tomorrow and go from there."