PEORIA, Ariz. -- On the same day that Mariners manager Dan Wilson announced how Seattle’s rotation will slot out to begin the regular season, the notable name absent among that group took the first big step in his rehab from the arm injury that will sideline him for the schedule’s first month.

For the first time in two weeks, George Kirby picked up a baseball on Friday morning.

“I wasn’t even thinking about my arm,” said the right-hander, who was shut down on March 7 with inflammation in his pitching shoulder.

Kirby played catch for roughly 20 throws at 60 feet with a member of the Mariners’ athletic training staff and will do so again on Saturday at 75 feet, after which he’ll transition to bullpen sessions, then, more than likely, live batting practice and/or extended spring training games on the Minors side.

The plan is for him to remain in Arizona for the next few weeks, but once those benchmarks are cleared, Kirby could then begin a Minor League rehab assignment with an affiliate -- most likely High-A Everett and/or Triple-A Tacoma given their proximity to Seattle.

The 2023 All-Star is optimistic that he could reach an 80-pitch threshold by late April, which would be the barometer for when he could return to the big league rotation.

“It’s definitely hard for me,” Kirby said of being sidelined and having to essentially start his throwing program from scratch. “But yeah, I’ve just got to take the time and understand my body these next couple weeks, just kind of get through it.”

Kirby received a biologics shot about a week and a half ago to combat the inflammation then was cleared to begin strength exercises a few days after.

“I’d say, overall, it's probably a more long-term thing,” Kirby said of the injection. “But I do feel a lot better right now. My tissues feel a lot better, more loose, all that kind of good stuff.”

The setback is more prolonged than Kirby initially envisioned but one that the Mariners opted for extra caution on, given that he’s a vital piece to the roster’s most valuable group and that it’s so early in the year.

Kirby was worth 4.2 wins above replacement last year, per FanGraphs, the most on the team and ninth-most in MLB, good for a 3.53 ERA (104 ERA+, where league average is 100), a 23% strikeout rate and 3% walk rate over a career-high 191 innings across 33 outings.

Yet as restless as the uber-competitive Kirby has been, he also pointed out that a delayed start to his season could also yield longer-term benefits.

“It might be a situation where the guys who've got five or six more starts than I do, I might be feeling a little better in October or whatever,” Kirby said. “But yeah, I'm just excited for when that happens.”

In Kirby’s stead and on the heels of a strong spring, Emerson Hancock will slot into Seattle’s rotation. Hancock will be inserted as the No. 5 starter and make his regular-season debut next Monday against the Tigers, following Logan Gilbert (Opening Day), Luis Castillo (Friday vs. A’s), Bryce Miller (Saturday vs. A’s) and Bryan Woo (Sunday vs. A’s).

Hancock made 12 starts last year -- and in the same role as an injury fill-in, for Woo twice then Castillo to finish the season -- going 4-4 with a 4.75 ERA. He’s always been affable, but there’s been a new level of confidence this spring.

“I think it’s a little bit of just being myself a little bit more,” Hancock said. “I think for a while, I just was trying to be so serious. And at the end of the day, it’s so much more fun when you’re out there enjoying it and you have freedom in what you’re doing.”

The Mariners are keeping their fingers crossed that this is just a health hiccup for Kirby, and they’ll lean on a familiar face to get by before his hopeful return.