SEATTLE -- Edward Olivares did not start Friday night’s game after he was recalled from Triple-A Omaha in a pregame roster move.

He didn’t have an at-bat, even, until all nine innings were complete and the Royals and Mariners played on in extra frames.

But Olivares ended up being a major part of why the Royals walked out of T-Mobile Park with an 8-7 victory over the Mariners in 12 innings, ensuring at least a series split in the four-game set this weekend.

“That was one of the wins I think this group will never forget,” manager Mike Matheny said after the 4-hour, 40-minute marathon that saw the Royals secure their 34th comeback win of the season.

The two-out, two-strike slider Olivares hit in the 12th inning off reliever Yohan Ramirez just barely cleared the left-field fence, grazing the glove of a leaping Jake Fraley as it dropped over for the decisive blast.

“We’ve watched him do that, even in deep counts, when he gets to two strikes, he just stays through the ball well,” Matheny said. “You've got to get it to get out of this park. You never know who’s going to be the hero.”

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Olivares was one hero Friday night. Salvador Perez was another. Trailing the Mariners early once again due to a shaky Royals start, this time from lefty Kris Bubic, Perez came to the plate with the bases loaded in the fourth inning. One swing off Mariners starter Logan Gilbert turned a four-run deficit into a 5-5 game.

And that’s where it would stay until the 10th inning because of the third hero of the Royals’ win: Carlos Hernández. The right-hander tossed 5 2/3 innings of relief, retiring the first 14 batters he faced and not having to work around a baserunner until the automatic runner in the top of the 10th inning. Hernández allowed one hit -- an infield single -- and saw the tying run score in the 10th on a sacrifice fly.

“I don’t know if we’ve seen something as impressive as what we just watched,” Matheny said of the performance. “[Hernández] looked as good as we’ve ever seen him. Just attacking the zone with every pitch. That was huge for him.”

Hernández was originally scheduled to start Saturday’s game. Understanding why he came in relief Friday has to do with the situation the Royals are in right now with their pitching staff. Before Brad Keller went on the injured list following Thursday’s start, the Royals were rolling with a six-man rotation that included Keller, Bubic, Hernández, Daniel Lynch, Brady Singer and Mike Minor.

Having six starters leaves the bullpen a pitcher short. And as the Royals finish up a stretch of 17 games without an off-day, the 'pen has been stretched thin. Almost every night, the next day’s starter is available in case of emergency innings.

“It’s been interesting,” Bubic said. “The preparation doesn’t change, because you still prepare for the five-day schedule. But any time your name is called to pitch, you go out there to get outs, regardless of what day it’s on or who you’re facing. That mentality has been important.”

Regardless of the club’s record this year, Matheny and the Royals have been committed to chasing every win they can to help build for the future. When Perez hit the grand slam to tie the game in the fourth inning, Matheny saw a path to victory. He needed a steady, trustworthy arm that could cover multiple innings while keeping the Royals in the game.

“We’re trying to be creative here in how we can get our guys the rest they need,” Matheny said. “Once Salvy hit that home run, we had a lot of game to cover, and Kris’ pitch count wasn’t going to go much further. And we didn’t want to not take advantage of the momentum that grand slam gave us.”

Hernández, who has experience in the bullpen, did just that, striking out six Mariners in 5 2/3 innings and joining Bubic as the only Royals this year to toss five-plus innings of relief without allowing an earned run.

“You always have to be prepared,” Hernández said through interpreter Luis Perez. “They gave me the heads up that I was going to be the emergency guy today, and it happened, and I was ready.”

Richard Lovelady took over to get two outs in the 11th, and Josh Staumont closed it out with 1 1/3 innings to earn the win.

Hernández’s outing moved everyone else up a day, so Lynch was sent back to the hotel early to prepare for Saturday’s start, with Singer scheduled for Sunday. But it’s likely not going to take Hernández out of the rotation. The Royals have an off-day Monday, and afterward, they can reset their rotation so everyone has the proper rest cycle between scheduled starts.

“At [that] point it doesn’t matter the situation,” Hernández said. “It’s about coming in and competing and helping the team get a win, whether I’m starting or relieving. It’s about being ready.”