Dave Roberts to reconsider how he uses left-handed reliever Scott Alexander

Dave Roberts said he will “rethink” his use of reliever Scott Alexander after the left-hander gave up another hit to a left-handed batter Saturday, a run-scoring single to Juan Soto in a five-run eighth inning of a 5-2 Washington Nationals win.

“He just couldn’t get his sinker down,” the Dodgers manager said of Alexander, who battled Soto to a nine-pitch at-bat. “It’s very uncharacteristic of [him to throw] repeated belt-line sinkers.”

Alexander’s splits have been strangely reversed this season — he has held right-handers to a .136 average (three for 22) but left-handers are batting .346 (nine for 26) against him. He held left-handers to a .172 mark and right-handers to a .288 mark last season.

“I think there’s a little something with Scotty’s [left] hip, his delivery, and he hasn’t had that consistent sinker or slider,” Roberts said. “We need him to get back to the form we’ve seen in the past.”

Alexander said the injury is more of a hamstring issue that arose two weeks ago in San Francisco.

“I was landing just short of the hole [on the mound] and I would slide out a little bit more, and I overstretched it, I overtweaked it,” Alexander said. “They did a good job of giving me a day here and there, but it’s just been a lingering thing.”

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With left-handers Caleb Ferguson and Tony Cingrani on minor league rehabilitation assignments, a roster move could be made this week.

“I don’t know yet if it’s something that’s affecting how I’m pitching, but that’s what we’re trying to figure out,” Alexander said. “I want to be out there, but if it’s one of those things where I’m not helping the team, it’s a perfect time to get it right.”

Until a move is made with Alexander, Roberts could expand the role of right-hander Pedro Baez, who, thanks to his improved changeup, has held left-handers to a .111 average (four for 36).

Roberts pulled Baez for Alexander in the eighth inning Saturday night. Alexander was replaced by Dylan Floro, who gave up a grand slam to Gerardo Parra.

“I like Scotty against lefties, so right now you have to continue to run him out there,” Roberts said. “But we have to get that delivery and execution right. We can look at the game situation [Saturday] night, and there’s a different way I could have gone, but I liked the matchup with Scott.”

Slump buster

Corey Seager entered Sunday mired in a 13-game skid in which he hit .125 (six for 48) with a .406 on-base-plus-slugging percentage, no homers, five RBIs, 13 strikeouts and six walks, dropping his season average to .225.

The shortstop drove in the team’s first run with a second-inning sacrifice fly to deep left field, and he knocked in four more runs with a game-breaking grand slam to right field in the eighth.

“It was a better day today,” Seager said. “I’ve been grinding pretty good. I put some good swings on it today. It was nice. It’s been a challenge so far, so hopefully it gets better.”

Short hops

Since the start of the 2018 season, left-hander Hyun-Jin Ryu is 11-2 with a 1.11 ERA in 15 starts at Dodger Stadium, striking out 106, walking seven and holding opposing batters to a .196 average in 97 innings. … With off days Monday and Thursday, Roberts will juggle the rotation so right-hander Kenta Maeda can start against San Diego’s predominantly right-handed lineup Wednesday night. Left-hander Rich Hill, who was in line to start Wednesday, will be pushed back to Friday’s game at Cincinnati. … Ferguson (rib-cage injury) will continue his rehab stint for triple-A Oklahoma City at Round Rock (Texas) on Monday. Ferguson threw a scoreless inning for Class-A Rancho Cucamonga on Friday.

mike.digiovanna@latimes.com

@MikeDiGiovanna