OAKLAND – Rookie right-hander Erik Swanson and utility man Kristopher Negrón were promoted by the Mariners from Triple-A Tacoma on Tuesday, while outfielder Mac Williamson was designated for assignment as the club’s roster churn continued.

Swanson fills a bullpen spot that opened on Monday when rookie relievers Parker Markel and David McKay were optioned to Tacoma, and right-hander Sam Tuivailala was activated off the 60-day injured list.

The Mariners already lead the Majors in players used this season with 53, as well as with most pitchers (35) and relievers (30). Tuivailala and Negron will increase those numbers once they make their season debuts, with Negron getting the start in Tuesday night’s series opener against the A’s in left field.

The team is closing in on the club record for players used in a season (61), which was set during in 2017. Additionally, Seattle has already used the second-most pitchers in a season in club history, trailing only the '17 record of 40.

The moves leave the Mariners with 39 players on their 40-man roster. They have seven days to trade, release or outright Williamson to the Minors.

Swanson went 1-5 with an 8.04 ERA in seven appearances for Seattle -- including six starts -- in April and May, but he has been pitching in relief in recent outings for Tacoma and will continue in that role with the Mariners.

“We’ll probably use him in more extended outings than just one inning,” manager Scott Servais said. “The plan is to be a multiple-inning guy who could work into an opener role. We’ll see what happens there.”

The 25-year-old pitcher (Seattle’s No. 9 prospect per MLB Pipeline) was acquired from the Yankees along with left-hander Justus Sheffield (No. 4) and outfielder Dom Thompson-Williams (No. 15) in the James Paxton trade last winter. Swanson has posted a 5.55 ERA in 24 1/3 innings over 10 outings for Tacoma, including six starts.

“Right now the role is just to be out of the bullpen. We’ll see what happens after that. I was doing some long relief stuff down there and an opener, throwing an inning or two,” Swanson said. “We’ve talked about the opener a little, but I think it’s just kind of keeping it as an option. I did it a couple times in Tacoma. It’s not too much different than starting, just a shorter start.”

Negron, 33, hit .207/.233/.310 in 29 at-bats over 18 games for Seattle last September after being acquired from the D-backs and has been in Tacoma all this year. Negron has posted an outstanding season in Tacoma, hitting .310/.396/.503 with 12 homers and 61 RBIs in 82 games.

While he can play all the infield positions, Negron will be used primarily in the outfield for now as the Mariners remain without Mitch Haniger and Braden Bishop. He’ll split time with rookie utility man Dylan Moore in left field and Negron's ability to play center field, should Mallex Smith need a day off, is a plus, according to Servais.

“Outfield is fun,” said Negron, who came up as a shortstop before developing into a utility player with the Reds and D-backs. “You get to run around and stretch your legs a little. But at this point, any position feels like home. I’m comfortable with all of them.”

Williamson arrived in Seattle with a bang, hitting a three-run home run in his first at-bat as a pinch-hitter in a 14-1 win over the Astros on June 5. But the 29-year-old posted just a .182/.276/.299 line with three home runs and 10 RBIs in 25 games.

Tuivailala ready to roll

The 26-year-old reliever’s long journey back from a ruptured Achilles finally ended as he rejoined the Mariners on Tuesday, almost a year since he was injured on Aug. 8 in his fifth game with the team last season after being acquired from the Cardinals.

“It kind of feels like I got my first callup again,” Tuivailala said. “I feel good, just trying to get back in the routine again. It’s been long. It felt like a wave. I had my good days and bad days. It was definitely a challenge, mentally and physically, but all that is in the past. I’m here now.”

Servais said fellow relievers Hunter Strickland and Brandon Brennan are also getting closer to returning, which would help the short-handed ‘pen.

Strickland, out since the end of March with a strained right lat muscle, will throw live batting practice in Tacoma on Wednesday and then begin a Minor League rehab stint if all goes well.

Brennan has missed the past month with a right shoulder strain, but he's been picking up the pace of his throwing program.

Felix Hernandez, sidelined for two months with a right lat strain, will throw his first full bullpen session on Thursday in Seattle as he tests his progress.

Haniger earns Heart and Hustle Award

Haniger was nominated as the Mariners’ 2019 Heart and Hustle Award winner by the MLB Players Alumni Association. The 2018 American League All-Star has been sidelined the past five weeks with a ruptured testicle and was scheduled to see the doctor on Tuesday in Seattle as he still is awaiting clearance to resume baseball activities.

“He had a great year last year and that’s one of the reasons we’ve talked about how we want to move forward with him and Marco Gonzales, just how they go about their business and being an advocate of what we’re trying to do here in going a different direction with our organization,” Servais said. “Unfortunately the injuries have taken a toll on Mitch this year. We’ll get him back eventually, but he’s very deserving of that award.”