An intriguing Spring Training battle has concluded on the field. Now the Mariners must decide who will fill the sixth and final spot in the rotation, Justin Dunn or Nick Margevicius.

Dunn entered spring as the favorite, given that he’s a right-hander in a lefty-loaded rotation and showed tangible physical improvements that were discussed during his exit interview last season. He remains a foundational piece of Seattle's rebuild.

Margevicius, a waiver claim from the Padres in 2020 who went on to become a pleasant surprise, has done nothing in Cactus League play to damage his standing, though he gave up four runs, five hits, two homers and two walks in 3 2/3 innings in the Mariners' 8-5 loss to the A’s on Thursday in his final outing of the spring.

• T-Mobile Park home to alternate training site in '21

Here’s the case pro and con for each:

Justin Dunn
What he brings: Pure stuff. Dunn’s fastball velocity was up to 96 mph after averaging 91.4 mph over his first two seasons, an uptick that was a direct byproduct of Dunn revamping his physical routine. He overhauled his diet after learning that he’s allergic to dairy, which led the New Jersey native to replace his favorite dish, New York-style pizza, with more vegetables.

His breaking pitches have been stellar at times, particularly during his seven-strikeout outing against the Cubs on Wednesday.

“I'm happy with where I'm at. … Fastball velo is still here,” Dunn said after that start. “Honestly, it feels like it's ticked up. The slider feel sharp. I’m really happy with the curveball shape and happy with the differential between the two.”

Areas for improvement: Command, as it has been since the 25-year-old made his Major League debut as a September callup in 2019. Dunn has walked 17.5% of the batters he has faced in the big leagues, the highest rate of 416 pitchers who have thrown at least 50 innings in that stretch. This spring, Dunn walked nine in 11 innings over four outings, including the leadoff batter in his final start on Wednesday.

If Dunn can hone his newly gripped changeup -- which he drew from Pedro Martinez, Frank Viola and Trevor Hoffman -- there’s potential for a true five-pitch mix.

“The changeup is going to be work in progress, obviously,” Dunn said. “But happy to have a weapon potentially to have later and towards the end of the year.”

Nick Margevicius
What he brings: Consistency, control and the ability to limit damage. Before Thursday, Margevicius hadn’t given up a homer all spring and had surrendered just one walk. Over his first three spring outings, the 24-year-old gave up two runs and nine hits over nine innings. In 2020, Margevicius gave up just six homers to 170 batters faced.

“I feel like I had a really strong spring,” Margevicius said. “I’m feeling confident with the stuff I worked on in the offseason, and that confidence kind of continued from every bullpen to my live BPs and each outing. The more confidence that I can build is the more comfortable with who I am as a pitcher.”

Areas for improvement: Continuing to polish his secondary pitches, specifically in trying to throw them for strikes. Margevicius throws in the low 90s and doesn’t generate much swing-and-miss on his heater -- all six of his homers in 2020 were against his four-seamer, and opposing hitters had a .269 batting average and a .529 slugging percentage against it, which indicates that his slider and curveball will be huge factors for his effectiveness moving forward. But both were strong in his 10 outings in ’20, with opposing hitters batting .162 and slugging .189 against both combined.

“Definitely, especially with my curveball. That’s something that I’ve been working on,” Margevicius said. “Not just that they want to see, but I know myself that’s something I need to do. I need to be able to get ahead with secondary stuff to keep hitters honest. I can’t rely on my fastball to get me a strike every time I need it.”

This isn’t an area of improvement, but one thing working against Margevicius is that he’s left-handed and Seattle already has four lefties -- Marco Gonzales, James Paxton, Yusei Kikuchi and Justus Sheffield -- locked for the Opening Day rotation.

The outlook
Beyond the decision of who breaks camp with the big league club, the Mariners will have to determine what to do with the other: Send that pitcher to the alternate training site, use him in the bullpen or, in what would seem like an outside chance, reassign him to Minors Spring Training.

Regardless of who breaks camp, the other candidate will contribute Major League innings this season.