SCOTTSDALE, Ariz. -- All-Star right-hander Hisashi Iwakuma, top pitching prospect Taijuan Walker and hard-throwing reliever Stephen Pryor were all placed on the 15-day disabled list Saturday by the Mariners, putting their roster at the final 25 heading into Monday's season opener in Anaheim.

All three moves are retroactive to March 21, meaning the three could technically return by the opening homestand on April 8 if they are ready. It's unlikely any of the three will be ready that soon, though Walker and Pryor both began throwing in Minor League games this past week.

Iwakuma, who was third in last year's American League Cy Young voting, was cleared by doctors on Friday to begin a normal throwing program as he begins to build his arm strength after missing all of camp with a torn extensor tendon in his right middle finger.

Iwakuma, 32, will accompany the team on the first road trip to Anaheim and Oakland so he can work with the team's trainers and begin throwing bullpen sessions after previously being limited to playing catch.

Walker, 21, was placed on the disabled list with a right shoulder impingement. He has pitched in Minor League intrasquad games, but did not appear in any Cactus League games after being shut down for a week at the start of March due to soreness that bothered him upon arrival at camp in early February.

Pryor, 24, was placed on the disabled list while recovering from surgery last August to repair a torn latissimus dorsi tendon in his right shoulder. He also has not appeared in any Cactus League games this spring, but pitched in Minor League intrasquad games.

General manager Jack Zduriencik said Walker will start the season on a rehab stint with Class A Advanced High Desert and Pryor will do the same with Double-A Jackson.