Ryan Brasier quickly turned into one of Boston’s most reliable late-inning relievers in the second half of 2018 after he had not pitched in the major leagues since 2013.

The righty posted a 1.60 ERA and 0.77 WHIP in 332/3 innings (34 relief outings) after his promotion in July. He then allowed just one earned run in 8 2/3 innings during the postseason.

Who might emerge for the Red Sox as an unexpected late-inning reliever in 2019? In other words, who could become the 2019 version of Ryan Brasier?

The 40-man roster is at 39 right now. The Red Sox are likely to acquire another major league reliever before they head to spring training in six weeks. David Robertson, a rumored Red Sox target, signed with the Phillies on Thursday, and the Yankees re-signed Zach Britton over the weekend. Adding a proven, reliable reliever is the most important remaining task for the Boston front office this offseason.

But the Red Sox also certainly have a few candidates who could emerge as pleasant surprises.

Boston signed Zach Putnam to a minor league contract last month. The 31-year-old righty missed 2018 after undergoing Tommy John surgery. This certainly is a low-risk, high-reward signing, like when Boston inked Brasier last March.

But Putnam, unlike Brasier, has enjoyed major league success. He has appeared in 145 games, posting a 3.20 ERA and 1.23 WHIP. He had a 1.98 ERA in 54 2/3 innings in 2014 with the White Sox.

Colten Brewer is another potential candidate to emerge. The Red Sox acquired the right-handed reliever from the Padres for minor leaguer Esteban Quiroz on Nov. 20. The 26-year-old has hurled just 9 2/3 career big league innings, all last year. He allowed six earned runs.

He’s another low-risk, high-reward acquisition. The Red Sox didn’t give up much for Brewer, and he has two minor league options remaining, so he doesn’t have to make the 25-man roster out of spring training. He can be optioned back and forth from Boston to Triple-A Pawtucket unlimited times in 2019.

“He’s got a plus-fastball, plus-breaking ball,” Red Sox President of Baseball Operations Dave Dombrowski said. “He pitched well at the minor league level. We have scouting and analytics that both like him. We think he’s a guy that has a legitimate chance to pitch for us. So we like a lot of things about him.”

Carson Smith is another candidate. Yes, that’s the same Carson Smith who suffered a right shoulder subluxation when he threw his glove in the dugout after giving up a home run to Athletics slugger Khris Davis this past May.

Smith has logged only 23 2/3 innings over the past three seasons because of Tommy John surgery he underwent in 2016 and shoulder surgery in 2018. The Red Sox outrighted him earlier this offseason, then re-signed him to a minor league deal.

The expectations certainly are low considering the limited innings he has pitched the past three years and how he’s returning from major shoulder surgery.

Travis Lakins, Darwinzon Hernandez and Josh Taylor, who have never pitched in the majors, all are candidates to fill important roles in the Red Sox bullpen. The Red Sox added all three to the 40-man roster in November to prevent them from becoming eligible for the Rule 5 Draft.

Lakins recorded a 1.21 ERA in 37 1/3 innings between Double-A Portland (21 innings) and Pawtucket (16 1/3 innings) in 2018. He pitched more than one inning in 11 of his 30 outings, including eight times in his final nine appearances. He recorded six outs in four outings. So he has a chance to become a multi-inning reliever, similar to the way the Milwaukee Brewers use Josh Hader.

The Red Sox plan for Hernandez to begin the year in the minors as a starting pitcher, but the Red Sox are willing to move him to the bullpen if the need arises, Dombrowski said. He finished the 2018 season in Double-A as a reliever for the Sea Dogs after making 23 starts for Class A Salem, going 9-5 with a 3.56 ERA and 124 strikeouts in 101 innings.

Taylor, a lefty, should receive an opportunity at some point in 2019 because he joins Bobby Poyner and Brian Johnson as the only left-handed relievers on the 40-man roster.

The 25-year-old spent most of 2018 with Portland and recorded a 2.10 ERA over his final 24 appearances (251/3 innings).

Durbin Feltman is the most well-known Red Sox minor leaguer not on the 40-man roster who could earn a setup role at some point in 2019. Many thought Feltman would be a September call-up in 2018 after the Red Sox drafted him 100th overall out of TCU in June. But Dombrowski and the minor league staff opted to take it slow with him. The righty finished with a 1.93 ERA, 0.99 WHIP, 36 strikeouts and five walks in 22 relief outings (231/3 innings) for short-season Lowell (four games), low-A Greenville (seven games) and high-A Salem (11 games).