PITTSBURGH -- Four games into the season, the Pirates are without three of their top four outfielders.

Pittsburgh placed left fielder Corey Dickerson, the club’s No. 3 hitter, on the 10-day injured list before Thursday’s series opener against the Reds due to a right posterior shoulder strain. The Pirates replaced Dickerson on the active roster by reinstating right-hander Jordan Lyles, Thursday’s starting pitcher.

“Nothing specifically caused it. I think it’s just a lot of stuff that we were doing,” Dickerson said. “It’s better to take care of it now to be able to help the team for as many months as I can at 100 percent, than try to manipulate and let it linger and not help the team as much as I want. I’d rather knock it out right now -- we’ve got more off-days coming up -- and just try to get it to 100 percent.”

The only projected Opening Day starter still standing in the outfield one week after the Pirates’ first game is center fielder Starling Marte. He’ll be flanked in the corners – for now, at least -- by some combination of Melky Cabrera, JB Shuck and Pablo Reyes. Shuck started in left with Cabrera in right Thursday.

Noticeably missing from the outfield mix are starting right fielder Gregory Polanco (shoulder), replacement right fielder Lonnie Chisenhall (fractured finger) and now Dickerson. It’s unclear how long the Pirates will have to get by without their injured outfielders, but none of them seems set to return soon.

Chisenhall only began gripping exercises Wednesday. Polanco is playing seven-inning games in extended spring training and has yet to start an official rehab assignment. Manager Clint Hurdle went out of his way to speak to Chisenhall when the team learned of Dickerson’s injury.

“You can’t hit an HOV lane on your recovery and your rehab because another guy went down,” Hurdle said. “We need you back when it’s appropriate, when you’re back to help the club.”

The Pirates could call for outfield reinforcements and send out one of their eight relievers this weekend, but they wanted to keep their bullpen full behind Lyles on Thursday.

“We want to cover our pitching right now and we’ll see where the next couple days take us,” Hurdle said.

Outfield prospect Jason Martin, the Bucs’ No. 11 prospect according to MLB Pipeline, is a likely callup candidate after being removed from Triple-A Indianapolis’ Opening Day roster Thursday. The 23-year-old slashed .325/.392/.522 in Double-A Altoona last season, then batted just .211 with a .589 OPS for Triple-A Indianapolis. Martin had an impressive spring campaign, however, going 7-for-23 with two homers and two triples while playing left and center field.

“If we’ve got to go another outfielder deep, we have internal options,” Hurdle said. “You also can look from your creative lens on what you can do with your active Major League roster to maybe get somebody else in play that’s had past experience to facilitate some help in the area of need.”

To that end, the Pirates asked reserve infielders Kevin Newman and Colin Moran to pick up outfield gloves. Newman has fielded fly balls the past two days, while Moran tracked balls hit by outfield coach Kimera Bartee in left field Thursday afternoon.

The Pirates are counting on Dickerson, who won his first Gold Glove Award last year, to be a steady presence in their lineup after he slashed .300/.330/.474 in 135 games last season. He pinch-hit Wednesday and will be able to hit with no restrictions, even as he is shut down from throwing for the next few days.

“Right now, we know that the timeframe is he’s going to be out for a minimum of 10 days,” director of sports medicine Todd Tomczyk said. “We’ll take things as they progress.”