The 25-year-old entered in a bases-loaded situation with no outs in the third after Elias struggled mightily in his final start of the season. The A's jumped to a 3-0 lead in the first on a three-run blast by Danny Valencia and Elias sandwiched a pair of walks around a base hit in the third before manager Lloyd McClendon called for Zych.
The hard-throwing right-hander induced three straight groundouts on six pitches to allow just one of Elias' runners to score, then zipped through the next two innings with just an infield single. He struck out the side in the fifth before turning a 4-3 deficit over to Mayckol Guaipe.
"I just tried to attack them and get a couple ground balls," Zych said. "I was hoping for maybe a double play or something there. It worked out. One got across, but it was still a pretty good inning."
It's been a pretty good month for the youngster as well.
"Unbelievable experience," he said. "Hopefully I'll just take it into the offseason and learn from everything. It's been awesome so far."
Zych made a spot start on Monday against the Astros, throwing 2 2/3 scoreless innings and has allowed just one earned run over his last 13 2/3 innings with 18 strikeouts and two walks. Saturday's outing was his longest yet after he came up primarily as a one-inning specialist.
"That's something that has been new, but it's starting to feel pretty good," Zych said. "I just try to give it one inning at a time. I don't know how long I'll go when I go in, but I just try to get outs and see what happens."
"He's done a nice job," said McClendon. "He's gone to the post a few times and done OK. I like what I see."
Zych is one of seven Mariners prospects earmarked to play in the Arizona Fall League, but said that is now under discussion due to the amount of work he's gotten in September.
"They said they'll let me know in the next day or so," he said. "Since I came up here I've got in a lot of games so far. I'll do whatever they want, but we'll see what they say."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB, read his Mariners Musings blog, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.