BOSTON -- Following the departure of Xander Bogaerts via free agency to the Padres in December, righty reliever Matt Barnes became the longest-tenured member of the Red Sox.

However, Barnes didn't hold that distinction for long. The Red Sox designated the veteran for assignment on Tuesday to make room on the roster for free-agent acquisition Adam Duvall.

The roster move came as a surprise due to the fact Boston has other relievers on the roster who are less proven than Barnes, a 2021 All-Star who is due to make $7.5 million in '23, the final year of his contract.

When a player is designated for assignment, he is immediately taken off the 40-man roster and the club has seven days to trade him or place him on irrevocable waivers.

Why was Barnes the odd man out?

"Obviously a really, really difficult decision," said Red Sox chief baseball officer Chaim Bloom. "The conversation itself [with Barnes] was one of the more difficult ones that I've had. Obviously the DFA process needs to play out, so there's a limited amount that I want to say about it until it does.

"But, you know, I think more than anything, this is just a function of where we're at in the offseason and with our 40-man roster. There are no easy decisions and regardless of recent accomplishments, regardless of what they have under their belts in their careers, everybody on our 40-man roster has real value.

"And so that forces tough choices, and it's obviously something we've been working through all offseason. And today we landed on Matt, but beyond that, it's certainly nothing negative about him. I think it's more a statement of where we're at with the 40-man roster, and beyond that I want to see the process play out first before saying more."

The Red Sox selected Barnes out of UConn with their first-round selection (19th overall) in the 2011 Draft.

A starter in college and in the Minor Leagues, Barnes turned into a reliever when he got his initial call-up in 2014 and remained in that role for years.

By 2016, Barnes became one of Boston's most trusted relievers, a distinction he carried for years.

He was dominant at times, particularly for Boston's 2018 World Series championship team. In that postseason, Barnes made 10 appearances and held opponents to a .103 average, giving up just one run in 8 2/3 innings.

In 2021, Barnes got the chance to become the full-time closer, and he initially excelled in the role, making the All-Star team and posting a 2.30 ERA with 23 saves through July 31. The Red Sox inked him to a two-year contract extension earlier that July.

Barnes struggled mightily down the stretch, posting a 9.26 ERA from Aug. 1 on and losing the closer's role

Those struggles continued into last season, but Barnes at last shook free from his slump after coming off the injured list in August. In his final 24 appearances of the season, Barnes had a 1.59 ERA.

He will now try to carry over that momentum with a new team.

The Red Sox will have a new-look bullpen in 2023, led by veteran closer Kenley Jensen and setup men Chris Martin and Joely Rodr¨ªguez.

Ryan Brasier, now one of just three holdovers from the 2018 title team, will also be part of the mix.

The Red Sox also have several hard-throwing young pitchers who will fight for spots in Spring Training.

"This is not an easy move, but one that we felt was the right one, and really isn't anything bad about Matt, who I'm sure is going to continue to have success in his career," said Bloom. "It was just a question of where we felt we were, how we see the 'pen coming together and what those other guys have a chance to do for us."