SEATTLE -- A White Sox team pondering its rotation for 2020 and beyond received some clarity Saturday night after Dylan Cease’s encouraging start at T-Mobile Park, though their one-for-one trade last Nov. 30 was at the center of the outcome.

Mariners catcher Omar Narvaez lifted a walk-off homer off White Sox reliever Alex Colomé (the player Narvaez was traded for in November) in the 10th inning on a play that ended in confusion.

The ball off Narvaez’s bat appeared to bounce off the exterior of the fence and back into play, but officials ruled that it was a homer, and the White Sox opted not to challenge if the ball cleared the wall, or if Narvaez touched home plate as he was mobbed by Seattle teammates.

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The club’s big picture focus, however, centered on Cease, who was scoreless through four innings and went toe-to-toe with Felix Hernandez on a night when the Mariners’ six-time All-Star looked like vintage King Felix. Cease labored to 106 pitches over five innings without great efficiency. But given where the rookie’s season was trending, Saturday marked a significant step in a positive direction.

“I always focused on the same thing, which is executing pitches," Cease said, "and I'm not going to be perfect, but that's why I'm here right now, to get experience and to go through the growing pains.”

Cease extended his career benchmark by reaching 135 1/3 innings for the season between Triple-A and the Majors, and the White Sox are steadfast that he will make his final two starts of the season, even as they have been cautious with his workload after he returned from Tommy John surgery in 2018.

The White Sox are eyeing a return to contention in 2020, and Cease figures to be a big part a rotation anchored by All-Star Lucas Giolito and supplemented by Reynaldo López and No. 2 prospect Michael Kopech when he returns from Tommy John surgery.

“We have guys with good stuff,” Cease said. “If we put it together, I think we can be really good. … I think you see spurts of it. This is a talented ballclub and we still have guys coming up, too. We're definitely seeing spurts of it.”

Over his most recent five starts, Cease had compiled an 8.22 ERA. On Saturday, he topped out at 97 mph, worked his way out of a bases-loaded jam in the fourth, limited lefties to 2-for-11 and pitched well enough to give the White Sox a chance to win, despite a stale offensive effort. But Cease also issued three walks, climbed into nine three-ball counts and has given up a homer in 12 of his 13 starts.

“Very deep counts, so it doesn't allow him an opportunity to stay in there for an extended period of time, which is what we need,” manager Rick Renteria said. “But encouraging, very, very encouraging -- even though it was a high pitch count, that he was able to do what he did and continue to try to work through the ballgame.”

Cease, who graduated from the Minors as MLB Pipeline’s No. 18 overall prospect and debuted on July 3, had a 6.53 ERA over his first 12 starts. His lone blemish on Saturday came via a solo homer in the fifth to Shed Long, who was the first batter Cease faced in his third time through the order. The White Sox are hopeful that, with improved efficiency, he might be able to work his way around a fourth time through in a similar scenario.