The Red Sox have designated Ryan Brasier for assignment, the veteran reliever told reporters (including MassLive.com’s Christopher Smith) following Sunday night’s 9-1 loss to the Cardinals at Fenway Park.

Brasier allowed three earned runs on four hits, no walks, and two strikeouts over a career-high 2 1/3 innings on Sunday. The right-hander gave up a run-scoring ground-rule double to Nolan Gorman and followed that up by serving up a 396-foot two-run home run to Nolan Arenado with one out in the top of the eighth.

Following Sunday’s performance, Brasier’s ERA on the season rose from 6.75 to 7.29 and his WHIP rose from 1.55 to 1.57 in 20 relief appearances (21 innings) for Boston this season. Needing to clear a roster spot for lefty reliever Joely Rodriguez, who is expected to be activated from the injured list on Monday, the Red Sox elected to move on from Brasier.

“Honestly, a new start might not be bad,” said Brasier, who was informed of the decision shortly after Sunday’s game ended. “Obviously getting to play at Fenway every day is a dream come true. Two parks you want to play at growing up are Yankee Stadium and Fenway. And I got to do both a lot. So grateful. It sucks obviously but new start.”

Brasier, 35, first joined the Red Sox organization as a minor-league free agent shortly before the start of the 2018 season. After spending the previous year pitching for the Hiroshima Carp of Japan’s Nippon Professional Baseball, the righty impressed in spring training and was called up by Boston for the first time that July.

Having gone nearly five years between big-league appearances, Brasier proved to be a major contributor out of the bullpen for the Red Sox during their historic World Series run. He compiled a 1.60 ERA in the regular season and allowed just one earned run over nine postseason outings (8 2/3 innings) in his first taste of October baseball.

Over the next two seasons (2019-2020), Brasier pitched to a 4.57 ERA in 87 total appearances (80 2/3 innings). He was limited to just 13 games in 2021 after missing the start of spring training due to a broken hand, beginning the season on the injured list due to a calf strain, and then being struck in the head by a line drive during a simulated game in Fort Myers.

Brasier was effective down the stretch in 2021 but that success did not carry over into 2022. He instead struggled to a 5.78 ERA in 68 appearances (62 1/3 innings). Though he made his fourth Opening Day roster this spring, it became increasingly clear that Brasier’s roster spot was in jeopardy as his struggles only continued.

“Walked a few guys early on, some bad luck,” Brasier said of his performance up until this point in the season. “A ton of (expletive) singles. This is what it is. I get it. It’s a business. And luck aside, I’ve gotta still have results to be at this level. And it just didn’t work out.”

Brasier does have a point as it pertains to bad luck. That much is made evident by his 4.39 FIP as opposed to his 7.29 ERA this year. Still, the majority of his other peripherals look far less encouraging and that likely played a role in Sunday’s decision.

Now that he has been designated for assignment, the Red Sox will have the next seven days to either trade, release, or waive Brasier, who is in the final year of arbitration eligibility (carries a $2 million salary) and was slated to reach free agency for the first time at the end of the season.

“Obviously, no hard feelings,” Brasier said. “Like I said, I know it’s a business. And things happen. But hopefully get picked up in a day or two and try to go win somewhere else.

“A couple tweaks, maybe somebody sees something that they think they can build on,” he added. “That’s all you can really ask for.”

Brasier, who turns 36 in August, forged a 4.55 ERA and 3.79 FIP with 211 strikeouts to 65 walks in 222 career appearances (one start) spanning 209 2/3 innings of work in a Red Sox uniform. He currently ranks 37th on the club’s all-time list for appearances.

With Brasier out of the picture, left-hander Chris Sale and third baseman Rafael Devers are the only players who remain from Boston’s 2018 World Series championship roster.

“Like I said, you grow up wanting to play at places like Fenway,” said Brasier. “And having a chance to do it for five years has been kind of surreal, honestly.”