WASHINGTON — There are days, such as Sunday in Pittsburgh, when Didi Gregorius feels like himself again. His feet are solidly underneath him. His hands move quickly. His body is in sync. And when that happens, he usually picks up a few hits, handles his chances at shortstop, and helps the Phillies win a game.

But for each of those days, there are many more when he feels lethargic, even weak, like he’s going in slow motion.

“I haven’t got my rhythm,” Gregorius said Monday before the Phillies opened a series here against the Nationals. “I haven’t got my rhythm in a while. I think that’s what’s missing. That’s what I’m trying to find.”

Gregorius isn’t sure that he will. At least not this season. He’s still taking medication to manage pseudogout, a rare condition that caused painful swelling in his right elbow and left him on the injured list for 49 days. There is no known cure, so for now, he said doctors want to continue to treat it with medicine because “otherwise it would swell back up.”

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The problem, according to Gregorius, is that the medication leaves him with an “energy level that’s draining.”

“Some days, I will feel like I don’t have anything because of the pills and everything that I’m taking for this,” Gregorius said. “And one of the big side effects is also muscle weakness, so you’ve got to work through all that, too. It is what it is. I’m not making any excuses, but that’s the boat I’m in right now.”

Perhaps it explains his performance. Since Gregorius returned from the injured list July 2, he is 17-for-90 (.189) with 4 doubles, 1 triple, 4 home runs, 17 strikeouts, and a .649 OPS in 25 games. In 228 plate appearances overall, he’s batting .212 with eight homers and 43 strikeouts.

Gregorius’ left-handed bat was the primary drawing card when the Phillies re-signed him last winter to a two-year, $28 million contract even though other free-agent shortstops (notably Andrelton Simmons, Marcus Semien, and Freddy Galvis) signed elsewhere for one year. But among 259 players with at least 200 plate appearances this season, Gregorius ranks 226th with a .638 OPS, well below his .741 career mark.

Defensively, the Phillies acknowledged that Gregorius‘ range was limited. But they believed he would make the routine plays and attempted to work on his positioning to help enhance his first-step quickness and enable him to get to more balls. Instead, he has been among the worst shortstops in baseball, with 11 errors in 56 games and the fewest defensive runs saved (minus-11).

Gregorius’ self-assessment: “It’s not where I want to be. One-hundred percent, I literally say I [stink]. I can just say that. I mean, it’s the truth.”

Indeed, Gregorius has been worse than a replacement-level player, according to both FanGraphs (-0.1) and Baseball-Reference (-0.7) WAR calculations. He has been outplayed by Phillies utilityman Ronald Torreyes.

Gregorius’s issues help explain why the Phillies acquired Galvis at the trade deadline last Friday.

Known for his dazzling defense from his first stint with the Phillies and popular in the clubhouse, Galvis batted .249 with nine homers and a .720 OPS in 72 games for the Baltimore Orioles this season. He has been sidelined since suffering a strained quadriceps June 26 but is expected to return later this month.

Galvis is a switch-hitter with stronger splits from the right side of the plate. Once he returns, it wouldn’t be a surprise to see him take some at-bats from Gregorius, who was already beginning to cede playing time to Torreyes against left-handed pitchers.

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How would Gregorius, an everyday player throughout his career, handle splitting time with Galvis?

“It’s going to help the team — that’s for sure,” Gregorius said. “That’s why he’s here. He’s going to help the team no matter what. Doesn’t matter where he plays: short, second, third, or whatever. If we have to move, it don’t matter. As long as we put up a ‘W’ and get into the playoffs. That’s the goal.”

But what about next season?

Gregorius, 31, is under contract for $14.5 million in 2022. He reiterated that he doesn’t know what caused the pseudogout, a “form of arthritis characterized by sudden, painful swelling” in a joint, according to the Mayo Clinic. He had never even heard of it before his diagnosis in June.

Regardless, his ability to manage it will determine the course of the rest of his career.

“Whatever they said that causes it, however I got it, I don’t do those things,” he said. “I don’t drink. I don’t eat red meat. So who knows how it got in my body? I don’t know. It doesn’t add up with my diet and everything I’m doing. It is what it is. It’s my job. I’ve still got to go out there and perform and just try to get better.”