Phillies’ Nick Castellanos headed for MRI after feeling ‘cramp’ in his right side

SAN FRANCISCO — Three hours before Saturday’s first pitch, Nick Castellanos changed into his street clothes and exited the Phillies’ clubhouse to go for an MRI.

On his balky toe?

“My oblique,” he said.

Castellanos left Friday night’s 13-1 loss in the sixth inning after feeling what he described as a “cramp” in his right side on a swing. An initial examination didn’t indicate a decline in strength, but the Phillies sent the right fielder for further tests for “precautionary” reasons, according to interim manager Rob Thomson.

» READ MORE: ‘Philly Rob’ has made all the difference for the Phillies, and history shows it’s a remarkable feat

The Phillies were still awaiting results of the test after Saturday’s 5-4 loss to the Giants, according to Thomson and Castellanos.

Asked if he was concerned about the outcome, Castellanos didn’t make a prediction.

“I have no idea,” he said. “We’ll see. I’ve never dealt with muscle stuff in my career. We’re just going to go get a picture and see what it looks like.”

In baseball, oblique injuries tend to linger because of the rotational stress of hitting and throwing. Castellanos also is dealing with turf toe, a condition that kept him out of the lineup for three games this week in Arizona.

Castellanos is batting .265/.305/.397 with 13 homers in 499 at-bats, less than the Phillies expected when they signed him to a five-year, $100 million contract in March. But he has been more productive recently. Since a game-winning homer Aug. 3 in Atlanta, he’s 28-for-96 (.292) with four homers and a .789 on-base plus slugging.

“There’s always concern, especially with the oblique,” Thomson said. “When it happened [Friday] night, he came to me and said he just felt it a little bit. I said, ‘That’s it. We’ll get you out.’ But he said he felt a lot better [Saturday]. We’ll make sure he’s OK.”

Without Castellanos, the Phillies are perilously thin in the outfield. Bryce Harper is limited to being a designated hitter by a ligament tear in his right elbow, leaving Kyle Schwarber, Brandon Marsh, and Matt Vierling as the only healthy outfielders. Vierling started in right field Saturday. Utility infielder Nick Maton also can play the outfield.

» READ MORE: Bryce Harper’s comeback success is ‘not an easy thing to do.’ Take it from Chase Utley.

At triple A, utilityman Yairo Muñoz is out with a bruised leg, while Símon Muzziotti is out for the season with a torn patellar tendon in his knee. Jhailyn Ortiz, the only other outfielder on the 40-man roster, is slashing .242/.324/.433 with 17 homers at double A.

Thomson said reports have been “really good” on nonroster center fielder Dalton Guthrie, who was batting .296/.358/.472 with 10 homers in triple A through Friday night. But the Phillies would have to clear a 40-man roster to call him up.

So, they’ll cross their fingers and hope Castellanos can avoid the injured list.

“It kind of just felt like a cramp,” he said. “No popping or anything like that. All that’s good. I passed all my strength tests and all those things. If there is anything, it’s going to be pretty minor. We’re going to see how it turns out.”

After throwing about 35 pitches and simulating a between-innings break in the bullpen Friday, Zach Eflin emerged without pain in his right knee.

Next up: Eflin is scheduled to face hitters Tuesday in a live batting practice setting at Citizens Bank Park. If that goes well, he could begin a minor league assignment.

It’s a stunning turn of events for Eflin, who appeared to be lost for the season because of pain around the surgically repaired patellar tendon in his knee. He hasn’t pitched in a game since June 25.

» READ MORE: Phillies prospect Griff McGarry moves to bullpen, pitches two scoreless innings for double-A Reading

If Eflin is able to return, it would be in a relief role. Thomson said the Phillies have not yet discussed how they may use Eflin or how his stuff may play up coming out of the bullpen.

But with Corey Knebel (shoulder) out for the season and Seranthony Domínguez dealing with triceps tendintis, the Phillies could use an extra late-inning arm. They moved prospect Griff McGarry to the bullpen in double A to determine if he may be a viable option down the stretch.

“We’ve got to get through this, and then we’ll start talking about roles and how we’re going to use him, what he’s comfortable with,” Thomson said.

Domínguez emerged from a bullpen session without issue. He likely will repeat the activity early in the week before going on a minor league assignment. ... High-A Jersey Shore outfielder Baron Radcliffe and double-A right-hander Andrew Baker were named Phillies’ minor league player and pitcher of the month, respectively, for August. ... Ranger Suárez (8-5, 3.42 ERA) is scheduled to start the series finale Sunday against Giants lefty Carlos Rodón (12-7, 3.03).