PEORIA, Ariz. -- The Mariners reassigned veteran outfielder Kirk Nieuwenhuis to Minor League camp on Tuesday, leaving just one decision -- the health of Ichiro Suzuki -- remaining before their final 25-man roster is set prior to Opening Day on Thursday.
In addition, the Mariners signed free-agent outfielder Jayson Werth to a Minor League deal, according to a source, as Seattle will see what the veteran has left at age 38. He will report initially to extended spring training in Arizona before being cleared to play in Triple-A Tacoma to start.
The decision on Ichiro will come after Wednesday's workout at Safeco Field. The 44-year-old went 0-for-3 with a walk in Tuesday's 5-3 victory over the Rockies in their spring finale.
Ichiro went hitless in 10 at-bats, with five strikeouts and two walks, in five Cactus League games while dealing with a sore right calf.
"I don't think he's quite at 100 percent yet, but he's moving much better and feels better out there," manager Scott Servais said. "We'll see how he feels tomorrow and make a decision from there."
Werth completed a seven-year, $126 million contract with the Nationals at the end of last season, but wants to continue playing after an injury-plagued 2017, during which he hit .226/.322/.393 with 10 home runs and 29 RBIs in 70 games.
:: Spring Training coverage presented by Camping World ::
The 15-year Major League veteran was a National League All-Star with the Phillies in 2009 and is a career .267/.360/.455 hitter, having also spent time with the Blue Jays and Dodgers. Werth was a full-time starter in '16 with the Nats, batting .244 with 21 homers and 69 RBIs in 606 plate appearances, but missed nearly half of last season with a fractured left foot.
"I don't have any history with him, but looking from afar, he's been on a lot of winning teams, he knows how to play, controls the strike zone very well and is a good veteran presence in the clubhouse," said Servais. "He was looking for an opportunity to extend his career and our group felt we had an opportunity for some at-bats at the Triple-A level. He hasn't had any Spring Training yet, so it's going to take him a little while, but I'm excited to have him in the organization."
Nieuwenhuis' departure leaves Seattle with 30 players in Major League camp, but four -- outfielder Ben Gamel, starters Erasmo Ramirez and Hisashi Iwakuma and reliever David Phelps -- will be placed on the disabled list before final 25-man rosters must be turned in to the league on Thursday morning.

Nieuwenhuis, 30, hit .250 with three home runs in 32 at-bats this spring since returning from a sore hamstring. The six-year veteran hit just .115 in 26 at-bats last year for the Brewers, but has played 414 games in the Majors with a line of .221/.311/.384, and started 92 games for Milwaukee in 2016.
The only remaining question revolves around the health of Ichiro, who has played sparingly since he signed on March 7. The club is still carrying two utility players -- Andrew Romine and Taylor Motter -- who can both play the outfield if needed.
Romine appears a lock to make the club, but Motter could also be kept if Ichiro isn't deemed ready. The other three outfielders on the club are Dee Gordon, Mitch Haniger and Guillermo Heredia. If Ichiro can't start in left field, Heredia will take his place.
The hope was that the 44-year-old could fill in on a regular basis in left field after Gamel strained his oblique muscle in early March, but he'll need to prove healthy to fill that role. Servais said before Tuesday's game that the biggest question was whether Ichiro could run well enough to cover ground in left field. He handled that relatively well with a couple catches in his eight-inning stint, but again was hitless at the plate with a strikeout, a lineout to right and an infield popout.
Seattle opens its season against the Indians on Thursday at 7:10 p.m. PT at Safeco Field, and the final roster must be set by 9 a.m. that morning.