The Pirates were hit hard by injuries this week.

Pirates director of sports medicine Todd Tomczyk said on Thursday that third baseman Ke'Bryan Hayes reaggravated his left wrist. Hayes, the No. 9 prospect in baseball, per MLB Pipeline, was placed on the 10-day injured list on April 4, after dealing with inflammation in the wrist that stemmed from a swing against Jake Arrieta the previous day.

The club also announced a flurry of moves on Thursday, including right-hander Chad Kuhl being sent to the injured list retroactive to Monday with right shoulder discomfort, and right-handed reliever Geoff Hartlieb being recalled.

Tomczyk also confirmed that Jared Oliva, one of the Pirates’ depth options in the outfield, will be out of action at the alternate training site for at least four weeks, after sustaining a left oblique injury. That news coincided with the club’s decision on Thursday to designate for assignment Dustin Fowler and recall Todd Frazier from the alternate training site.

Hayes was expected to see game action with the alternate site team in Toledo, Ohio, on Tuesday and Wednesday, but both games were canceled due to weather. Tomczyk said Hayes traveled to Detroit on Wednesday to take “high-velocity swings,” and the discomfort cropped back up while taking an awkward swing at a pitch.

“He felt it on the same swing when he had to awkwardly extend his wrist as he did during the game in Chicago,” Tomczyk said. “... That's what makes [rehab games] such an important part of the rehab process, because what we don't want to do is put Ke'Bryan in a position in a game where that would make the magnitude even worse, not only for him, but for the team as well.”

After struggling through a six-game losing streak once Hayes, who was a preseason favorite for the National League Rookie of the Year Award, was out of action, the Pirates’ top of the order has managed to produce good performances recently. Still, Hayes’ return would be a boon for an offense that ranked 19th in the Majors in OPS (.686) entering Thursday’s action.

“The main message for him was just stay positive,” manager Derek Shelton said. “We're 19 games into the season. Let's stay positive. Let's reassess and move on and see where we're at."

Shelton said Kuhl’s shoulder issue was something he and the Pirates monitored closely, and after some conversations Thursday morning -- and ahead of Kuhl’s scheduled start on Sunday -- they felt it was best to make the move now.

“It was just something that lent itself after his last start,” Shelton said, “and with the discomfort, going to Minnesota, it being cold and the off-days coming up, we just felt that it was the best opportunity to give him a little bit of a break.”

The Pirates are still determining how best to fill Kuhl’s turn in the rotation on Sunday, but Shelton pointed to Luis Oviedo, Sean Poppen and Duane Underwood Jr. as options to provide length in a potential bullpen game if needed.

As far as the outfield shakeup, Fowler slashed .171/.239/.195 in 18 games as the Pirates’ center fielder, where he split time with Anthony Alford, who was designated for assignment on Wednesday.

“We gave a couple of guys opportunities and felt like it was time to adjust and move,” Shelton said. “We move forward.”

How so? For now, it won’t involve Oliva, the Pirates’ No. 16 prospect per MLB Pipeline, who joined the alternate training site squad last week after working on “skills development” in Bradenton, Fla., to begin the season. He felt pain in his oblique during batting practice and alerted the medical staff before being shut down.

In the short term, the Pirates will play Bryan Reynolds in center field, as they did in Thursday’s series finale against the Tigers.

“That’s not to say he’s going to stay in center for the rest of the year or every day,” Shelton said, “but I would say in the short term, you’re going to see him in center.”

Ka’ai Tom will also have a great opportunity to claim the job of starting center fielder. The Pirates claimed Tom off waivers on Wednesday from the A’s, who had selected him off waivers in the Rule 5 Draft this offseason.

Brian Goodwin, an experienced option at all three outfield spots, is at the club’s alternate training site, but Shelton said the Pirates made the move for Frazier instead on Thursday as he was a “better fit” for the coming games. Shelton said Frazier will be an option to cover both infield corners, though he served as the DH on Thursday in Detroit ahead of another American League set with the Twins.

”I think it’s something that we felt would put us in a better situation, yeah,” Shelton said of the move for Frazier. “So once we found out about Key, we decided to make a retro move on that.”