Miller (oblique) to start rehab, but where will he fit with Hancock shining?

SEATTLE -- Bryce Miller rejoined the Mariners on Friday at T-Mobile Park, where he played catch as part of a final tuneup before beginning a Minor League rehab assignment.

That first outing will be Saturday with Triple-A Tacoma, general manager Justin Hollander said before Seattle’s series opener against Texas.

Miller, who’s been recovering from a left oblique strain, will need the full 30-day allotment that is granted for pitchers during this stint to build workload, given that the issue initially surfaced during his first Cactus League start on Feb. 26 and he hasn’t pitched in a game since.

More broadly, the Mariners might have the best problem the sport has to offer on their hands when Miller is ready to return: the possibility of possessing more than five capable and healthy starters.

“If we get a month from now, and that's what happens, we'll figure it out,” Hollander said. “We haven't made any decisions on that whatsoever. And truthfully, like, God bless us if it is a problem 30 days from now.”

That discussion began mostly as murmurs over the season’s first three weeks but has grown into a more prominent conversation given the consistency of Emerson Hancock, who broke camp in the rotation in Miller’s absence but has posted a 2.28 ERA over his first four starts.

Despite a potential logjam, the Mariners are looking at Miller’s situation completely independent of Hancock.

“I don't really think it's a great way to make decisions if we let what's happening in the big leagues dictate rehab schedules,” Hollander said. “If things weren't going well -- let's say we had another starting pitching injury, or we had a starting pitcher that wasn't reforming -- it still probably wouldn't be wise.

“So as much as you try not to let those things dictate what you're thinking or what you're feeling from a medical perspective, our medical team won't even allow us to go down that road.”

Miller will essentially go through a full Spring Training-type buildup, consisting of a six-day routine and beginning with two innings and/or 30 pitches. Typically, starters make about five such starts before the regular season and are prepared to go 5-6 innings and/or 80-90 pitches. Miller’s assignment will flip-flop between Tacoma and High-A Everett, depending on which team is at home.

Hancock has been the Mariners’ de facto injury replacement within their rotation for the past three years, taking over for Miller when the club broke camp.

But this stretch has felt different. He’s racked up a team-best 29.4% strikeout rate (nearly 13 points higher than last season) and a 4.7% walk rate (3.1% lower than last season and second-best on the team), while holding hitters to a .512 OPS (also second-best).

“I don't really think about it a whole lot,” Hancock said. “I just get out there, I have a job to do. I have a really good process and a good plan. And I have really good catchers that are bought into that plan.”

For fans clamoring for Luis Castillo to be the odd man out, that’s just not going to happen.

Despite an 8.03 ERA in his past three outings, he’s been their most durable arm over the past three seasons, eclipsing 30 starts and 175 innings each year with a 3.50 ERA in that stretch. He’s also their highest-paid player ($24.15 million this year and next), and they can’t simply option him to the Minors.

Even with Castillo’s hiccups, Seattle’s rotation entered Friday leading MLB with 3.1 wins above replacement, per FanGraphs, and 118 1/3 innings. Their 3.35 ERA coming into the day was seventh-best.

As for Miller, he said his oblique has felt “100 percent” for the past 10 days or so, after experiencing tertiary discomfort in the days after some throwing sessions since the Mariners broke camp. But those issues have subsided.

The progression of his buildup will be just that -- focused on arm strength capable of handling a Major League workload.

“Mainly, just go out and attack how I will in-game,” Miller said. “I'm not trying to add any pitches or do anything crazy. Just go out and let it rip. And now that the oblique is healed up, and I'm past that, it's just getting back on a routine and feeling normal.”