BALTIMORE—When the Orioles’ series with the Boston Red Sox began on Friday, they were still on a high after John Means’ no-hitter in Seattle two days before. Those positive feelings have vanished after three tough losses to the Red Sox.

The latest, a 4-3 setback on Sunday before 10,274 at Oriole Park on Mother’s Day, was perhaps the toughest to take.

Orioles starter Dean Kremer pitched well for five innings, but he didn’t get much support on offense or in relief and, after winning the first three games of the season against Boston (22-13) at Fenway Park, the Orioles have lost six straight. The teams conclude their four-game series on Monday night.

“They’re a really good team,” said first baseman Ryan Mountcastle, who drove in two of the Orioles’ three runs. “Really good lineup, really good pitching staff. It’s going to be a battle every time we play them. Hopefully, we can turn things around tomorrow.”

Hits were difficult to come by for the Orioles against Boston starter Nick Pivetta.

“When you get four hits, you don’t expect to win the game,” manager Brandon Hyde said.

After Boston rightfielder Hunter Renfroe robbed Austin Hays of an extra-base hit with a leaping catch in right field in the first, Trey Mancini and DJ Stewart walked. Mancini then scored on an RBI single by Mountcastle.

Boston third baseman Rafael Devers hit his eighth home run of the season with one out against Kremer in the second to tie the score. Five of Devers’ eight home runs have come against the Orioles.

Centerfielder Cedric Mullins homered with two outs in the fifth, his sixth of the season, to give the Orioles a 2-1 lead. It didn’t last long.

After Kremer limited the Red Sox to three hits and one run through five innings, he gave up hits to Marwin Gonzalez and Adam Verdugo to begin the sixth. Hyde summoned Adam Plutko and, for the second straight game, an Oriole reliever allowed the inherited runners to score; Shawn Armstrong did the same the night before.

Plutko walked J.D. Martinez to load the bases with one out and struck out Xander Bogaerts before Devers drove a double to deep center to score two runs for a 3-2 Red Sox lead. Plutko retired Renfroe and Bobby Dalbec on ground balls to shortstop Freddy Galvis to end the inning.

“I was encouraged by Dean’s start once again,” Hyde said. “I thought he threw the ball really well. I liked the aggressiveness on his fastball.”

Kremer (0-3) was charged with three runs on five hits in five-plus innings. He acknowledges he’s learning on the major league level.

“Obviously, the competition’s harder,” Kremer said. “You’ve got to lock it in, and you can’t take any breaks, mentally or physically. Our staff has been awesome. Every guy, pretty much, I’ve learned a little bit from, whether they’re a bullpen guy, a starter guy, even position players.

“My dad, before the season and last season, was like, ‘don’t get too caught up in start-to-start. This is a small blip in your career.’”

Pivetta (5-0) gave up two runs on three hits in six innings,

The Orioles (15-19), who are four games under .500 for the third time this season, had a final shot against Pivetta in the sixth. Stewart walked, and Ryan McKenna, who was pinch-running, drew a pickoff throw, which was wild and allowed him to advance to second.

Stewart was pulled because of a strained left hamstring, the same injury that caused him to most of spring training and to start the season on the 10-day injured list.

Mountcastle struck out and Galvis flied to center, ending the sixth.

Josh Taylor walked Pedro Severino to begin the seventh, but he was doubled off on Rio Ruiz’s liner to second. It was the second time the Orioles made that kind of baserunning mistake in the series; Mullins was doubled off on Friday night on a liner to right by Mancini. Pat Valaika walked after the double play, but Mullins struck out to end the inning.

Renfroe hit a 453-foot home run to center in the eighth against Cole Sulser for a 4-2 Boston lead.

Adam Ottavino began the last of the eighth by hitting Hays with a pitch. He moved to third on two infield outs and scored on Mountcastle’s double to center. Galvis grounded to second for the third out.

Matt Barnes pitched a spotless ninth for his eighth save.

Tate to injured list: Right-hander Dillon Tate was placed on the 10-day injured list retroactive to Saturday because of a left hamstring strain. Tate’s injury was sustained covering first base in Friday night’s game. Hyde said Tate “did the splits” covering first.

“He went for treatment that night,” Hyde said. “Yesterday, it was a little bit sore. We just wanted to see how it was going to be the next couple of days, but it’s still really sore.”

Tate is 0-1 with a 3.46 ERA in 11 games.

The Orioles recalled McKenna from Triple-A Norfolk. It’s his third stint on the club.

“Mac’s going to give us a little help position player-wise just because we are a little banged up in the field, too,” Hyde said. “We have some guys playing through some stuff. Ryan adds an extra body for us, position player-wise. I’m sure there are more moves on the horizon.”

Franco sits: Maikel Franco, who is in a 3-for-38 slump to drop his average to .210, didn’t play.

‘Nothing wrong with him physically, just giving him a day,” Hyde said. “He’s scuffling at the plate. I want to give him a day to sit back and relax.”

Lowther to bullpen: Hyde said that Zac Lowther, who allowed seven runs in 2 1/3 innings in his first major league start on Saturday night, will go to the bullpen for now.

The Orioles have offdays on Thursday and May 17.

Valaika takes mound: Valaika, who started at second base, pitched the ninth inning for the Orioles on Saturday night. It was his first time pitching.

Valiaka threw five pitches to four batters. Ramón Urias committed an error on Valaika’s first batter, Renfroe.

“I’m impressed with Pat Valaika and the first-pitch strikes,” Hyde said. “I’ll take that position player outing, hopefully not too often.”

Hyde approached Valaika in the sixth or seventh to ask about pitching.

“I didn’t get the greatest reaction back,” Hyde said. “I was hoping for more of a reaction.”

Fredi Gonzalez, the coach who stands next to Hyde during games, got a better reaction when he talked to Valaika in the eighth. Gonzalez told Hyde that Valaika was excited for his chance.

“Boom, he’s in,” Hyde said.

Notes: Galvis has a 10-game hitting streak. … Jorge Lopez (1-3, 6.49 ERA) will face Martin Perez (0-2, 4.40) on Monday night in the series finale against the Red Sox. … The Orioles are 4-13 at home.