SEATTLE -- When Hisashi Iwakuma re-signed with the Mariners after seeing his December agreement with the Dodgers fall apart, an interesting situation emerged. A team with five solid starters after the acquisitions of Wade Miley and Nathan Karns suddenly was looking at six prime contenders.
And that rotation battle, determining the chosen five heading into the regular season, figures to be a main focus of Spring Training once pitchers and catchers report to Peoria, Ariz., this Friday.
"I think there's going to be a great competition for the fifth spot in our starting rotation," said general manager Jerry Dipoto. "The fact that I think we have minimally six, and perhaps up to eight or nine legitimate candidates for the Major League rotation is excellent. The fact that our fifth or sixth starter may be physically as gifted as most people's two or three, that's exciting to me."
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The pitching picture can change in a hurry if injuries strike, but heading into camp the Mariners are confident that veterans Felix Hernandez, Iwakuma and Miley will occupy three of the five spots. And that leaves three youngsters who still have Minor League options -- Taijuan Walker, James Paxton and Karns -- vying for the last two.
Realistically, it's hard to imagine Walker not being one of the chosen five as the 23-year-old oozes with potential and rebounded from a slow start to go 11-8 with a 4.56 ERA in his first full year in the rotation last season. But Walker isn't taking anything for granted.
"It's always compete mode," Walker said. "At any given time, someone can come take your spot. I feel like with baseball, you're never safe. Obviously there are guys like Felix who have been around for 10 years and done it a long time, but being a young guy you've still got to go out and compete."

Paxton, the lone lefty outside of Miley, certainly has the ability to grab the remaining spot if he stays healthy. The 27-year-old is 12-8 with a 3.16 ERA in 30 career starts, but was limited to 13 games in each of the past two years due to a lat injury in 2014 and a finger problem in '15.
"It's time for me to show I can last an entire season and not have any of these weird injuries anymore," said Paxton, who has lost 20 pounds this offseason and is feeling more athletic. "Knock on wood, hopefully I'm done with those and can just move forward."
Karns, 28, went 7-5 with a 3.67 ERA in 27 games (26 starts) in his first Major League season as a regular starter for the Rays last year and was the centerpiece of a trade that cost the Mariners young shortstop Brad Miller, first baseman Logan Morrison and reliever Danny Farquhar, so he'll certainly be given a shot to show what he can do as well.
Dipoto notes that it always takes more than five starters to get through any season, and building organizational depth was one of his first goals. The Mariners also have lefties Vidal Nuno and Mike Montgomery returning and acquired Joe Wieland from the Dodgers.
Nuno figures in the bullpen mix unless the rotation is racked by injuries. Montgomery -- who is out of options -- will begin camp as a starting candidate, but could be tried in the bullpen if that appears to be a better opportunity.
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"We're going to take the best five pitchers we feel that can help us win games," Dipoto said. "Right now, going in, Taijuan Walker made great progress the last two-thirds of last year. I think you started to see some of what he was capable of, and we want to see him take one of those jobs. Similarly, James Paxton has shown that he's capable of being elite when he's out on the mound. We need to make sure he's out on the mound. That's a positive.
"Nate Karns is coming off a really good year, spent a full season in the big leagues and had a very nice season for the Rays last year. If you take pitchers who threw at least 147 innings, Nate Karns was one of the top 20 in the American League in ERA and was among the top half-dozen in strikeouts per nine. Those are feats, particularly when you pitch in the American League East. It's a nice problem, to have six Major League starters with some stake on the jobs, and it's going to be nice to watch the competition."
Pitchers and catchers report
Friday
Full squad reports
Feb. 24
First Spring Training game
Home vs. Padres, March 2, 12:10 p.m. PT
Opening Day
Away vs. Rangers, April 6, 1:05 p.m. PT