Are rotation hiccups a cause for concern?

This story was excerpted from Daniel Kramer’s Mariners Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

SEATTLE -- Although it's been a frustrating start for the Mariners’ retooled offense, the stumbles from their pitching staff -- particularly a rotation touted by many entering the year to be among MLB’s best -- have been surprising and somewhat startling.

Even including Bryce Miller’s seven scoreless innings on Friday, the rest of Seattle’s starting five -- Luis Castillo, George Kirby, Logan Gilbert and Emerson Hancock -- carried a combined 7.82 ERA the second time through. They gave up six homers, and opposing hitters had a .339 batting average and .589 slugging percentage against them -- all MLB worsts in that stretch.

These numbers don’t include Castillo’s outing in Monday’s series opener in Toronto, which itself was another uneven performance not accustomed to the consistency that “La Piedra” has shown. To be sure, it’s a wildly small sample.

But coupling the rotation’s challenges from last week with the bullpen’s hiccups -- Andrés Muñoz’s uncharacteristic meltdown on Friday, and Austin Voth and Gabe Speier’s precarious outings that nearly led to a Brewers comeback on Saturday -- is not a formula for sustained success. It’s no coincidence that the Mariners' only win the second time through was via Miller’s gem, and even that was put in peril.

A few things could be in play, and they all vary by each arm.

Castillo: He was on cruise control last Tuesday against Cleveland until an 0-2 count with two outs in the top of the fourth that Will Brennan turned into an RBI double after three straight fouls. Then, two pitches later, Bo Naylor took him deep for a two-run homer that became the game’s turning point. Castillo couldn’t recover, and he wound up surrendering five more hits before leaving at 5 2/3 innings. It also didn’t help that he received zero run support.

Kirby: He played catch-up at the outset last Wednesday, surrendering a base hit to Steven Kwan on the game’s first pitch and rolling his eyes at himself for it. His defense then made one blunder after another to put the game out of reach before Kirby could work his way into a rhythm, yet he pitches with more emotion than any among this group and is admittedly trying to be better when trouble arises.

Gilbert: His stuff was there on Friday in Milwaukee, with 13 whiffs and seven strikeouts, but the Brewers made him pay on each of his mistake pitches, for a career-high-tying three homers. Gilbert has always been susceptible to the long ball -- the 29 against him last year were tied for ninth most in MLB -- and outings where he’s taken deep put the onus back on the offense, as Seattle is 9-11 in his career when he gives up at least two in a start.

Miller: There was a ton to like, especially as Miller held Brewers left-handed hitters a combined 0-for-13 after getting tagged by lefties last year for a .917 OPS, compared to a .549 OPS from righties. He effectively worked both his fastballs at the top and bottom edges, then went to his new splitter as his primary out pitch. He was so good that there were questions as to why he was pulled at just 78 pitches, though with it being this early in the season, it’s clear why.

Hancock: A few defensive lapses behind him prolonged the jams he found himself in, but his biggest issue was effectively landing his pitches at the bottom of the zone. Because Hancock doesn’t possess elite velocity, it’s vital that he hits his spots, and when he doesn’t, outings like the one on Sunday (eight runs in 3 1/3 innings) can persist. There’s also the underlying factor that he’s trying to prove himself while taking Bryan Woo’s spot as he recovers from right elbow inflammation.

This is hardly time to panic. Castillo and Kirby were both All-Stars last year, Gilbert is in that territory, Miller’s massive adjustments since debuting last May have paid off and Hancock did pitch well in his ‘24 debut.

But Seattle’s blueprint for success starts with this group, and extended hiccups from the majority of these five on any given turn defies their path to success, and it showed with a 1-4 record the second time through, and reached 1-5 after Castillo’s outing on Monday against the Jays.