SEATTLE -- Logan Gilbert looked like he was on the cusp of perhaps his most dominant outing of the young season early on Wednesday, yet a few command issues continued to creep into his delivery during a costly fourth inning that proved to be a decisive sequence in a 4-2 loss to the Phillies.

Gilbert, who was hitless to that point, gave up a leadoff single to Alec Bohm, walked Bryce Harper and Jean Segura, and then served up a belt-high fastball to red-hot Rhys Hoskins, who crushed a 367-foot grand slam that gave the Phils all the cushion they needed -- particularly given that the Mariners’ bats continued to struggle with run production. 

“I gave up too many runs and walked too many people,” Gilbert said. “But like I said, the stuff felt the best it's felt all year.”

Other than that costly sequence, Gilbert was solid, with a career-high-tying nine strikeouts and only two other hits allowed. Yet the free passes that preceded the slam were perhaps more pressing given that his walk tally has significantly trended up since he was named the AL Pitcher of the Month for April. 

After giving up just one walk in his first three starts combined, Gilbert has surrendered 13 in four outings since -- with at least three per start in that stretch. He walked three or more just three times in his 24 outings in his promising rookie season last year. 

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It’s translated to a 14.6% walk rate since these issues surfaced, dating back to April 26 at Tampa Bay, which is among the highest for MLB starters in this stretch. However, Gilbert believes he’s corrected some of the issues he had with arm-side misses in his recent outings, and he was mostly back on track other than the 18 pitches he threw from the start of the fourth, which led to Harper’s walk, to the slam. He went on to strike out each of the next four hitters.

“He was frustrated with himself,” Mariners manager Scott Servais said. “He knows he had really good stuff today, and to let it slip away from him like that in that inning, disappointing.”

Gilbert has held opposing hitters to a .197 batting average and .289 slugging percentage during his past four starts, but also a .315 on-base percentage, which heavily contributed to Hoskins being in position to deliver a big blow on Wednesday. The Phils’ slugger has also been on the cusp for some time, and he homered in each of the three games this series.

Gilbert also didn’t have much in the way of his slider on Wednesday. He threw it 13 times over his 95 pitches, generated five swings and zero whiffs. It also accounted for one of his walks, below the zone, to Segura. Gilbert developed a much harder, tighter slider over the offseason in an effort to better diversify his repertoire after becoming so fastball-reliant last year.

“My fastball was the best it’s felt all year,” Gilbert said. “I was on line, over the top, backspinning the ball. I'm not really flying open like it was in the past, so I don't think that was a problem. The fastball felt pretty good. I think they had some good takes, especially on the slider, where we were trying to get chases when I got to two strikes that they might flinch or whatever but didn’t go for.”

The good news is that Gilbert looked and felt dominant. The bad was that his brief moments of vulnerability were far too much for a struggling Mariners offense to overcome. After Wednesday, Seattle has scored two runs or fewer in 14 of its 32 games this season.

Both of the Mariners’ runs came from RBI singles, via Julio Rodríguez in the third and Ty France in the seventh. After France’s knock, Rodríguez stepped to the plate as the go-ahead run with runners on the corners, but he popped out to finish a competitive, seven-pitch at-bat against Jeurys Familia.

The Mariners are off on Thursday for the first time in 16 days. Seattle then embarks on a three-city, 10-game road trip, beginning against two juggernauts, the Mets and Blue Jays. They’ve hit .204/.281/.328 on the road for a .609 OPS that is fifth-lowest in the Majors, and they’re cognizant that they’ll need to turn that around quickly if they’re going to get back on track.

“We need to hit on the road,” Servais said. “I've often said, to win on the road, you’ve got to hit on the road, so we need to pick it up offensively for sure.”