SEATTLE -- The offseason is winding down, and the Mariners have a fairly different look than when they wrapped up the 2020 campaign more than four months ago. After seeing much of their young nucleus begin taking steps forward in a shortened season, the Mariners are now looking to continue adding pieces in order to begin a legitimate push to contend for a postseason spot in 2021.

General manager Jerry Dipoto believes he already has many of the key players in place, either on the roster or waiting in the wings in the Minors, after several offseasons of significant turnover.

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Things have been a little quieter this winter, but the front office has nonetheless been active -- and that could continue into camp. What are the Mariners¡¯ biggest needs? MLB.com will keep track here over the offseason, so check back for updates.

BIGGEST NEEDS

Bullpen
This has been by far the area of greatest concern for Seattle, and Dipoto said last fall that he would like to add three or four experienced relievers to a group that had the highest bullpen ERA (5.92) in the American League in 2020. He did so by acquiring right-hander Rafael Montero -- who was 8-for-8 in save opportunities as the Rangers' closer last season -- with his first trade of the offseason.

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Dipoto also brought back Kendall Graveman in a relief role and upside piece Keynan Middleton, whom Dipoto originally drafted in 2013 when he was the Angels GM. The club also signed familiar face Roenis Elías to a Minor League contract, with hopes that he can recover from an elbow injury that, along with a positive COVID test, kept him sidelined with the Nationals in '20. And just before camp, Seattle signed veterans Taylor Guerrieri and JT Chargois on Minor League deals with a chance to compete for depth spots. Its flashiest free-agent acquisition has been top-end reliever Ken Giles, though he will be recovering from Tommy John surgery for all of '21.

In house, three rookie relievers -- right-handers Joey Gerber and Yohan Ramirez and lefty Anthony Misiewicz -- stepped up last season, and there are interesting prospects like Sam Delaplane, Wyatt Mills and Aaron Fletcher who will have an opportunity to make an impact in ¡¯21.

Another starter
The Mariners got through the shortened season with their rotation largely intact, and they will return Marco Gonzales, Yusei Kikuchi, Justus Sheffield, Justin Dunn and Nick Margevicius, who combined to start 47 of the team¡¯s 60 games. That group will be supplemented by offseason signee Chris Flexen?to comprise a six-man rotation that Seattle plans to stick with for the 2021 season.

An early neck issue with Graveman and a midseason trade of Taijuan Walker led to a very young rotation by the second half, but Sheffield, Dunn and Margevicius all performed well as 24-year-olds, and Gonzales turned in a stellar season in the No. 1 role. With pitching prospect Logan Gilbert knocking on the door, that group appears close to being set. But given the lack of experienced arms beyond Gonzales and Kikuchi in terms of workload limits, the Mariners could benefit from another innings-eater. Such an acquisition would also help bridge the gap to Gilbert and other up-and-coming prospects like George Kirby and Emerson Hancock.

Outfield depth
This doesn¡¯t loom as a big need, but Dipoto has said in recent weeks that the club could benefit from the addition of a left-handed bat that could play left field until No. 1 prospect Jarred Kelenic assumes that post, which figures to be at some point soon.

The Mariners got through last season by frequently deploying utility infielders Dylan Moore, Tim Lopes, Dee Strange-Gordon and José Marmolejos in corner-outfield spots.

Along with Kelenic, Taylor Trammell and Julio Rodriguez are also highly regarded outfield prospects, though Rodriguez likely needs more Minor League development. Jake Fraley and Braden Bishop are also in the mix, but given the uncertainty of how Mitch Haniger bounces back after missing the past year and a half, Seattle would benefit from an additional outfielder who can bat left-handed. That could become tricky, though, given that rosters are going from 28 players back to 26, and Seattle plans to carry 14 pitchers, which would leave them with just three bench spots (not including the backup catcher).

MOVES MADE

Feb. 11: Agreed to terms with standout reliever Giles
The Mariners' most prominent move of the offseason was more about setting up for 2022 and beyond. The club agreed to a multiyear deal with veteran Ken Giles, who was one of the most dominant closers in baseball before undergoing Tommy John surgery in October. In his last fully healthy season in '19, Giles racked up 23 saves and 83 strikeouts in 53 innings, posting a 1.87 ERA and a 244 ERA+ for the Blue Jays.

Feb. 10: Invited Guerrieri, Chargois to Spring Training
Seattle made a few late additions to its camp roster by bringing in veterans Taylor Guerrieri and JT Chargois, both of whom were prized prospects in the Rays and Twins organizations, respectively, earlier this decade. Both will compete for depth spots on the big league roster, and if they don't break camp with the club, they'll be needed as reinforcements for Triple-A Tacoma.

Jan. 7: Signed three to Minor League contracts
The Mariners brought back reliever Roenis Elías, who came up with the club as an international free agent in 2011, and signed Paul Sewald and infielder Jantzen Witte to Minor League deals. El¨ªas, who is coming off a strained flexor in his elbow, could have a chance to contribute Major League innings if he's able to regain the command and effectiveness that he showed during his last stint with Seattle in '19, when he compiled a 3.64 ERA with 14 saves in 28 outings. Sewald and Jantzen Witte figure to provide depth at Triple-A Tacoma.

Dec. 18: Added Flexen to rotation
The Mariners liked what they saw from right-hander Chris Flexen in Korea so much last year, they signed the 26-year-old to a two-year, $4.75 million free-agent deal, with an option for a third year. Flexen didn¡¯t put up great numbers with the Mets in his initial years as a promising prospect, but the 6-foot-3, 250-pounder went 8-4 with a 3.01 ERA in 21 starts for the Doosan Bears in Korea and now will get a strong shot to land one of Seattle¡¯s rotation berths.

Dec. 16: Signed Middleton to one-year deal
Dipoto drafted Keynan Middleton when he was Anaheim¡¯s GM in 2013 and now brings the 27-year-old to Seattle as a late-innings relief option. With a 97-mph fastball, Middleton has closer capability and was in that role for the Angels in 2018 until undergoing Tommy John surgery.

Dec. 15: Traded for Rangers¡¯ closer
Dipoto dipped into his young group of pitching talent to acquire Rafael Montero from the Rangers, giving up 17-year-old right-hander Jos¨¦ Corniell and a player to be named for a 30-year-old who has thrown well for Texas the past two seasons since recovering from Tommy John surgery. Corniell was Seattle¡¯s No. 24-ranked prospect, per MLB Pipeline, but Montero offers immediate help in the bullpen as a late-inning option with a 96-mph fastball.

Dec. 10: Added reliever Vest in Rule 5 Draft
For the third straight year, the Mariners used the Rule 5 Draft to add an intriguing arm, this time selecting 25-year-old right-hander Will Vest from the Tigers. Vest figures to have a good shot at earning a spot in the bullpen, as the Mariners are intrigued by a fastball that ticked up to 96-98 mph during instructional league action this fall in Florida, as well as a changeup they felt was one of the best in the Minor Leagues when he was pitching in 2019 at the Class A Advanced, Double-A and Triple-A levels.

Dec. 7: Reacquired Robert Dugger off waivers
The Mariners were involved in a trio of waiver moves, claiming Dugger from the Marlins while losing fellow right-handed pitchers Walker Lockett to the Blue Jays and Ian Hamilton to the Phillies. Dugger, 25, provides some starting depth as he¡¯s pitched in 11 games for Miami over the past two seasons, including eight starts, with a 7.40 ERA in 45 innings. He was drafted by Seattle in 2016 and traded to the Marlins prior to the '18 season as part of the Dee Strange-Gordon deal.

Nov. 20: Added four prospects to 40-man roster
In order to protect them from the Rule 5 Draft, the Mariners promoted center fielder Taylor Trammell and right-handers Juan Then, Sam Delaplane and Wyatt Mills to their Major League roster. All four are rated among Seattle¡¯s Top 30 prospects by MLB Pipeline and would have been eligible to be taken by other teams in the Dec. 10 Rule 5 Draft.

Oct. 29: Re-signed Kendall Graveman
After choosing not to exercise a $3.5 million option for Graveman, the 29-year-old right-hander was brought back on a one-year, $1.25 million contract that includes a potential $2.5 million in additional incentives if he pitches well in a relief role.

Oct. 23: Claimed Domingo Tapia
The 29-year-old right-hander with a 99 mph fastball was added to the bullpen mix as a waiver wire pickup after being designated for assignment by the Red Sox.