SEATTLE -- The Mariners reinstated three players -- outfielder Mitch Haniger, catcher Tom Murphy and reliever Andres Muñoz -- from the 45-day injured list to their 40-man roster on Sunday as the final bit of housekeeping heading into the Hot Stove season.

The open season for free agency began at 2 p.m. PT on Sunday for all Major League teams, though things could move slowly in that arena given the uncertain financial and health situations surrounding baseball and the country in the ongoing coronavirus pandemic.

While Sunday marked the deadline for numerous roster requirements as well as the opening bell for free agents to sign with other teams, Mariners general manager Jerry Dipoto had already taken care of most of his necessary roster maneuvering.

The Mariners opened space for Haniger, Murphy and Muñoz by outrighting five players off the 45-day IL over the previous week.

Four of those five -- relievers Nestor Cortes, Carl Edwards Jr., Matt Magill and Gerson Bautista -- are now Minor League free agents, while lefty Taylor Guilbeau was claimed off waivers by the D-backs.

Haniger and Murphy both are expected to be integral parts of next year’s club after missing all of this past season. Haniger has undergone three surgeries since rupturing a testicle on a foul ball on June 6, 2019, and he sat out the '20 campaign while recovering from a herniated disc, but Dipoto expects the 29-year-old to be full-go as the club’s starting right fielder by Spring Training.

Murphy, 29, also sat out all of last season while dealing with a broken bone in his left foot. He figures to split time behind the plate next year with 24-year-old Luis Torrens, who was acquired from the Padres on Aug. 31 and played well over the final month of the season.

Muñoz was also part of that seven-player swap with Torrens, and he could be an intriguing part of the bullpen once he’s recovered from Tommy John surgery. The 21-year-old flashed a 100-mph fastball for the Padres as a rookie in 2019 while posting a 3.91 ERA with 30 strikeouts in 23 innings.

With Haniger, Murphy and Muñoz reinstated, Seattle’s 40-man roster now sits at 35. That leaves Dipoto room to add several prospects who might need to be protected from the Dec. 10 Rule 5 Draft, as well as space for free-agent or trade additions.

Dipoto has said he’d like to add three or four experienced relievers to his bullpen mix, and the club already re-signed free agent Kendall Graveman to a one-year, $1.5 million deal on Wednesday after choosing not to exercise his $3.5 million option for 2021. Teams had a five-day window to re-sign their free agents prior to Sunday.

Sunday was also the deadline to exercise or decline all contract options, with the Mariners already declining options for both Graveman and second baseman Dee Strange-Gordon, who received a $1 million buyout in lieu of a $14 million extension for 2021.

Strange-Gordon and reliever Yoshihisa Hirano are the only two players from Seattle’s season-ending 40-man roster who are now hitting free agency. It figures to be an interesting offseason for the more than 160 MLB free agents, given the uncertain times coming off the shortened 60-game season, in which teams played without fans in the stands, and no guarantee how things will unfold in 2021.

That environment made it easy for Graveman to accept Seattle’s $1.5 million offer, with another $2.5 million in possible incentives, after the club declined his $3.5 million option.

“Even though I’m taking less guaranteed, it’s still a blessing for myself and my family and it puts us in a good spot,” Graveman said. “It’s humbling, for real. For somebody to think enough of me to give me a chance to continue to pitch is special and to know where we’re going to be in Spring Training and live during the season and all those thoughts that go through your head that a lot of people on the outside don’t understand when you need to move your family and all that. Knowing I’m going back to Arizona [for Spring Training] and Seattle is such a relief.”