Dustin Pedroia goes on DL; Joe Kelly sent down

Dustin Pedroia drove in two runs on a single in the sixth inning Wednesday night, but was injured running to first base and left the game. Barry Chin/Globe Staff/Globe Staff

The struggling Red Sox took another hit Thursday when their leader, Dustin Pedroia, went on the disabled list, the biggest in a series of roster moves necessitated by injuries and poor performance.

Pedroia was placed on the 15-day DL with a strained right hamstring, which means Brock Holt will be the primary second baseman and Pawtucket call-up Deven Marrero (.241, 4 homers, 21 RBIs) acting as the utility infielder.

“I’ve never pulled a muscle before,” Pedroia said. “It’s just kind of weird, right before I hit the bag my foot kind of slipped out and I hit the bag with my left foot. I tried to recover and stop. So I slipped basically. Those are things you can’t prevent. It’s frustrating mentally.

“You work hard in the weight room in the offseason trying to prevent injury and then little things happen. It’s tough but we’ll get through it. Guys will come together and hold it down until I get back and then we’ll go.

“Deal with it the best you can. Can’t dwell on it. It’s part of the game, I guess. You guys know me, I’ll be back as fast as I can.’’

What will the loss mean for the Red Sox?

“He’s the heart and soul of our team in the short description of it. The way he plays, what he means in the clubhouse, what he means on the field with his performance. Probably having a career year to date,” manager John Farrell said.

Mike Napoli said of Pedroia’s absence, “It’s gonna be tough. He’s one of our leaders, comes through in the clutch. Plays the game the right way. Guys are just going to have to pick it up. It’s that simple.”

Kelly sent down

In another move, starter Joe Kelly (2-5, 5.67 ERA) was optioned to Pawtucket. That means both players acquired in the John Lackey deal (also Allen Craig) are now in Triple A.

Justin Masterson will start Sunday vs. the Rays at Tropicana Field, but Farrell did not commit beyond that start.

There had been some speculation that lefthander Brian Johnson might get the call after another strong outing in Pawtucket Wednesday in which he went 6⅔ innings, allowing just one hit vs. Rochester. Johnson is 8-4 with a 2.57 ERA.

“He’s been throwing the ball well all year,” Farrell said. “There wasn’t a thought going in, because if we were going to make a move coming out of Joe’s start it was going to be with Justin first and then we’ll see where we go from there. But Brian’s doing a heck of a job and he’s been consistent at Pawtucket. When the opportunity presents itself remains to be seen. But with each passing start he’s getting closer.”

The Red Sox designated catcher Erik Kratz for assignment and brought up righthanded reliever Jonathan Aro. They also recalled Jackie Bradley Jr. who had two hits (snapping an 0-for-30 stretch dating to last season) and started a great double play with a good throw to the plate from right field. Bradley hit .322 with four homers, 16 RBIs, and an .867 OPS at Pawtucket.

Farrell said the team did discuss options for Kelly to either send him down or demote him to the bullpen. They chose to keep him as a starter to work out the kinks.

“It’s certainly not stuff, it’s not athleticism. The frustrating part of this, even for Joe and for all involved, is that when you see an athlete of his ability and it doesn’t translate to the consistent command of his pitches. That’s what is continually being addressed,” Farrell said.

Farrell said Kelly understood the decision and part of the demotion will be to learn to repeat his delivery and keep his emotions in check, something he didn’t always do from the bullpen to the actual game.

“Throwing your bullpen is one thing. In the heat of the moment, it’s a completely different story. And that’s where the control of the emotion and sometimes when the effort spikes, a guy comes out of his delivery a little bit and that’s where the mislocated pitches come in to play,” Farrell said.

Ramirez is better

Hanley Ramirez avoided the disabled list after being struck by a batted ball in the left hand Wednesday. Ramirez said he felt much better Thursday and hoped he would be able to grip a bat by Friday.

“I’m really surprised how it feels good today. It’s much less pain and I feel better [after] last night,” Ramirez said.

Some were critical that Ramirez got hit with the ball as runners are supposed to peek toward home plate when running to second.

“I peeked once, and I think it was a little bit early,’’ Ramirez said.

“When I was trying to peek a second time, just the ball was on top of me. So nothing I could do.”

He said it could have been worse.

“Yeah. That’s why I was a little scared last night before the X-ray. Everybody who saw it knows, you know. You can see it in the face, it was really bad. It’s going to be day-to-day. Treatment, ice. And, like I said, if I come tomorrow and I can grip the bat, I’ll be in the lineup.”

Debut day

Aro made his major league debut and went 1⅓ innings, allowing four hits and one run. Farrell called Aro, who had a 1.61 ERA at Pawtucket with 30 strikeouts in 22⅓ innings and just three walks after being called up from Portland, “a righthander that has moved quick. He was impressive in the couple of games in which he pitched in spring training. He’s a strike thrower, he’s got some swing and miss to his fastball. Doesn’t fear contact, evident by what the strikeout to walk [ratio is] at both Double A and Triple A this year. And is a young guy that’s on the move pretty quick here.” . . . Farrell called Marrero a “polished infielder. The bat came along a little bit in spring training with his ability to drive the baseball a little bit more consistently. But, primarily has been a shortstop through his pro career, always been a very, very good defender. He’s got some exposure both at second and third recently. And he has shown a lot of instincts in the games that we saw in spring training. So we’re fully confident and comfortable with him in this role.” . . . Portland center fielder Manuel Margot has been selected for the Futures Game during the All-Star break . . . Shane Victorino, recovering from a calf injury, played right field and went 2 for 3 with a double, a run, and an RBI in Pawtucket’s 6-5 loss to Rochester. Fellow rehabber Ryan Hanigan (knuckle) caught five innings and went 0 for 2 . . . The Red Sox signed draft picks Daniel Zandona (righthander, 21st round), Max Watt (righthander, 22d round), and Kyri Washington (outfielder, 23d round). Boston has signed 19 of its 39 selections.