Didi Gregorius raised his right arm to reveal the “huge bump,” in his words, on the outside of his right elbow that has caused him to miss three games and likely will keep him out of the Phillies’ lineup through the weekend.

Here, though, is the thing that most concerns the shortstop: He doesn’t know why the bump is there.

Gregorius sat out three games last month with elbow inflammation after landing hard on his right arm while pursuing a pop-up in shallow center field in an April 16 game against the St. Louis Cardinals at Citizens Bank Park. He received treatment for the swelling, including the draining of fluid from his elbow, and returned to play 17 of the next 19 games, missing time only after getting hit by a pitch April 28 in St. Louis.

But his elbow “flared up out of nowhere,” he said, Wednesday night in Washington. The swelling returned, leaving him unable to fully bend his right elbow. Although he said it doesn’t prevent him from throwing, he has had difficulty following through with a swing.

“To be honest, I don’t know what’s going on,” said Gregorius, who has three hits in his last 25 at-bats, dropping his average to .229 and OPS to .630. “It’s like so swollen. The first time we drained it. This time we’re letting it work its way out. We’re going about it day by day and try to get better and see how it goes.”

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Manager Joe Girardi said the Phillies remain hopeful that Gregorius will not need to be placed on the 10-day injured list, a move that could be backdated to May 13. But Gregorius said he’s scheduled to get an MRI exam and other testing when the Phillies return home Monday. It seems likely a decision to place him on the injured list could come after that.

Gregorius, diagnosed 10 years ago with a manageable kidney condition, revealed last month that it tends to take him longer than most people to get rid of inflammation. It isn’t unusual for him to be swollen for two weeks after getting hit by a pitch.

But that doesn’t explain why the swelling in his right elbow seems to have returned after subsiding.

“I don’t know if it’s the same thing and it happened again. We’re trying to figure out why it came back again,” Gregorius said. “I haven’t gotten a word on what exactly it is.”

Is he concerned?

“I am worried,” he said, “because I haven’t been on the field. I haven’t been playing. And the last time I played, my swings weren’t looking really good because I couldn’t extend my arm.”

After the initial injury, Gregorius underwent both an X-ray and an MRI to be certain he didn’t damage his ulnar collateral ligament, which was reconstructed as part of Tommy John surgery in 2019. The Phillies are confident that the swelling, which is located in a different area of the elbow from the UCL, is unrelated.

“A lot of people have asked me if it’s my Tommy John arm,” Gregorius said. “Yes, but it’s nothing to do with my UCL. It’s on the outside part of my elbow.”

Rookie infielder Nick Maton filled in for Gregorius again Saturday night against the Toronto Blue Jays in Dunedin, Fla. After making his major-league debut last month, Maton went going 15-for-42 (.357) with five doubles in his first 12 games. But he was 5-for-29 (.172) with one double and 11 strikeouts in 11 games through Friday night’s 5-1 victory.

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With Gregorius seemingly unavailable to pinch-hit, the Phillies’ bench consisted of catchers Andrew Knapp and Rafael Marchan and utilityman Scott Kingery, who was 1-for-14 with eight strikeouts and would be much better served going back to triple-A Lehigh Valley to recover his wayward swing.

A shorthanded bench is less consequential for the Phillies this weekend because they have a designated hitter for interleague games against the Blue Jays. But they will return to National League play Tuesday night at home against the Miami Marlins.

“I’m trying to be back on the field as quick as I can,” Gregorius said. “Me, as a player, I hate sitting out. I want to be back on the field playing.”

Extra bases

Reliever Archie Bradley allowed one run on two hits and one walk in a minor-league rehab appearance for Lehigh Valley. Bradley, sidelined since April 11 with a strained oblique muscle in his side, could be reinstated from the injured list this week. ... With victories in Atlanta on May 7, Washington on May 11, and Dunedin on Friday night, the Phillies won three series-opening games on a road trip for the first time since July 2016, according to the Elias Sports Bureau. ... Chase Anderson, who pitched for the Blue Jays last season, is scheduled to face his former team Sunday in the series finale. He will be opposed by lefty Robbie Ray.

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