PEORIA, Ariz. -- Outfielder Kyle Lewis, the Mariners' top-ranked prospect according to MLB Pipeline, is not among the 40-plus players who began a Minor League mini-camp at the club's Peoria Sports Complex on Monday, as general manager Jerry Dipoto said he's recovering from arthroscopic surgery on his balky right knee.
The 22-year-old Lewis had a cleanup procedure on his knee about 10 days ago and isn't expected to be on the field until the end of April. The hope now is that the procedure will take care of Lewis' ongoing issues since major surgery following a home-plate collision in 2016 just a month after he was selected with the 11th pick in the 2016 Draft.
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Dipoto said the club should know more after Lewis reports to Minor League camp on Thursday.
"There was kind of a floating piece of bone that was pinching off or creating a problem," Dipoto said. "It explains why he was having so much pain. Hopefully we are able finally to determine the source of the irritation and move forward in a productive way."
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Lewis played 49 Minor League games last season after rehabbing from his initial surgery to repair a torn anterior cruciate ligament as well as a torn medial meniscus and lateral meniscus. He was shut down again after feeling some discomfort during the Arizona Fall League, then had further problems after trying to gear back up this winter.
"Kyle has a chance to be a really good player," said Dipoto. "The fact that he's been frustrated by this, very few people in our organization work harder than Kyle Lewis. And he's had to because of what he's encountered so early in his career. He's been great about it. And we are hoping this is the final step to getting him healthy."
No firm timetable on Erasmo
Dipoto acknowledged there's no certainty that right-hander Erasmo Ramirez will be ready for the start of the season after being diagnosed Sunday with a strained lat muscle in his right side.
The hope is that Ramirez can be cleared to start throwing again after a two-week shutdown, but that's the best-case scenario based on the 27-year-old catching the injury before it got worse.
"As we know from having dealt with Evan Scribner the last couple years, lat issues can become bigger or long-term issues," Dipoto said. "Hopefully we caught this one early enough that it's short to mid-term. We don't know yet. We're hoping in two weeks we get a thumbs-up and he's ready to roll. But that's not a slam dunk. Then we have to take it day by day."

Dipoto said having Ariel Miranda and Andrew Moore as potential fill-ins means the club will stay in-house for solutions while Ramirez is sidelined. Additionally, a favorable early schedule would help if he's not initially ready.
"The great benefit we have, roughly for the first five weeks of the season, we have a day off about every week," Dipoto said. "That means we can be somewhat creative in how we get through with our starting rotation, if we need to start with Erasmo [on the disabled list].
"What would be more damning is if it's a long-term issue, and that is something we're going to have a tough time absorbing. So in the short term, we believe he'll be back and we're hopeful that's in two-three weeks. But over the long haul, we have to be prepared if it's longer than that."
Healy could be late arrival as well
First baseman Ryon Healy is projected to be out four to six weeks following Wednesday's surgery to remove a bone spur in his right hand, and there's a good chance he won't be ready when Seattle opens regular-season play on March 29.
"Whatever time it takes to get him back, we'll take that time," Dipoto said. "We're more concerned for the long haul."
Dipoto said veteran non-roster invitee Matt Hague is a candidate to fill in until Healy's return, as well as rookie left-handers Mike Ford and Daniel Vogelbach.
Healy did check in to camp for Monday's physicals. All 25 position players reported on time, including newly signed outfielder Junior Lake, who agreed to a Minor League deal.
Combined with the 32 pitchers and six catchers already in camp, that group will take the field Tuesday for the first full-squad workout leading up to Friday's Cactus League opener.