PEORIA, Ariz. -- Mariners right-hander Taijuan Walker, one of the top young pitching prospects in baseball, will be shut down from throwing for the next seven days after tests revealed inflammation in the bursa in his right shoulder.

"This definitely stinks," Walker said Friday. "But I feel good about the situation. I would rather not push it and try to fight through something and make it worse. I'd rather take the time off and just get healthy first and then move on."

Walker, 21, is the No. 6-ranked prospect in baseball this preseason by MLB.com, and he is expected to challenge for a spot in the Mariners' rotation after starting three games for Seattle at the end of last season.

Manager Lloyd McClendon said Walker has been put on anti-inflammatory medications after being re-evaluated by Dr. Neil ElAttrache at the Kerlan-Jobe Clinic in Los Angeles on Thursday. Walker has been held back since the start of Spring Training after arriving at camp with soreness in his shoulder, throwing just a couple of bullpen sessions and playing some flat-ground catch in recent days.

"It's a little bit of a setback, yeah," said McClendon. "But it is what it is and we just have to continue to move forward."

Will Walker have time to be ready for the start of the season if all goes well when he's cleared to throw again in a week?

"I'm not sure," McClendon said. "That's my hope, but we'll see how it goes."

Trainer Rick Griffin said it's impossible to put a timeline on a potential return at this point, considering the youngster will have to build his arm strength back up without feeling any discomfort at every step in order to keep the green light on.

"He is not going to throw for seven days. So when he starts again, he'll play catch and he'll need pain-free sessions," Griffin said. "Then he'll long toss, then several bullpens -- all the other guys here did three bullpens and two live batting practice sessions -- so I'd expect he'll need to be able to do the same. Then after the live batting practice, we'll set up simulated games either against our guys here or in Minor League games."

There has to be rest days between sessions and any issues will cause the Mariners to immediately back off.

"It really is the old day-to-day thing," Griffin said, which means a lot of eyes will be on Walker as he proceeds.

Walker said he can't worry about pushing for the opening rotation, but just getting healthy and keeping a big-picture outlook.

"I was looking forward to trying to win a rotation spot this season, but it is what it is," he said. "I'm behind a little bit, but I'll fight my way back up."

The Mariners will proceed carefully with the youngster from Yucaipa, Calif., who was the 43rd overall selection in the 2010 First-Year Player Draft and has since developed into one of the prized young arms in baseball.

"This guy, we're not just talking about 2014," McClendon said. "Hopefully, we're talking about the next 15 years. We have to be cautious and we have to be smart. It's frustrating for him, but I think it's the best avenue to take. Err on the side of being cautious and continue to move forward with it."

McClendon believes the issue cropped up from just normal throwing, and there's no indication of more extensive problems in the shoulder. Walker said the shoulder had been nagging him for the past two weeks, so he's relieved that tests showed no significant damage.

"The MRIs were clean and good," he said. "There's no structural damage. Everything is fine from that standpoint."

The Mariners have been without standout right-hander Hisashi Iwakuma since the start of camp due to a sprained tendon in his right middle finger. Iwakuma will see the doctor Friday afternoon for his three-week re-evaluation. He was initially expected to miss four to six weeks.

With both Iwakuma and Walker up in the air, the Mariners have some rotation openings behind ace Felix Hernandez.

"A lot of opportunities," McClendon said. "We have a lot of big arms to hopefully take advantage of those opportunities. We'll see what happens. Like I've said, I just hope they don't all eliminate themselves. Then we've got problems."

Right-hander Matt Palmer, a non-roster invitee to camp, has also been shut down for a few days with a slight elbow strain. Right-hander Brandon Maurer, however, threw well in his first bullpen session Thursday after being held out with a stiff back. Maurer appears ready to resume his normal schedule, McClendon said.

The Mariners' rotation was already somewhat up in the air beyond Hernandez and Iwakuma. Walker is among a handful of youngsters competing for a spot, along with James Paxton, Erasmo Ramirez, Blake Beavan and Maurer.

Veterans Scott Baker and Randy Wolf are in camp as non-roster invitees, coming back from Tommy John surgeries in 2012. Baker will make his first spring start Saturday against the Angels at Peoria Stadium, while Wolf is slated to start Sunday against the Indians in Goodyear, Ariz.

Palmer and Mark Rogers, a former Brewers first-round pick, are also in the mix.