And while Diaz coughed up the lead in one of his rare blips, the rest of the bullpen applied the clamps again with a perfect 10th by Drew Storen before Nick Vincent earned his third save of the season with a scoreless 11th.
Diaz had allowed just two hits and one run with no walks and 11 strikeouts in his previous nine September outings, but the 22-year-old really is still learning on the job. And despite his third blown save in 20 chances, the Mariners picked him up in this one.
"He's a young kid and he's going to have a bump here or there," said Vincent. "But the kid has electric stuff. I think that's what motivated me even more. It was like, 'You guys don't score runs off Diaz. That doesn't happen. You guys get two runs, sorry. If you get it off him, you're not getting 'em off me. It's not going to happen.'"
Vincent maneuvered through the same heart of the order that got to Diaz, allowing one-out singles to Jose Altuve and Carlos Correa before nailing down the final two outs.
"Nick has been really good,," manager Scott Servais said. "Our whole bullpen has. When we went through Eddie, we were holding Nick back so if we had [another] chance to close it out, we wanted him in there. We felt good about him. He's been throwing the ball really well and has a lot of confidence right now."
Vincent had a 2.19 ERA and opponent's batting average of .186 over his last 11 games and he's been strong since a midseason hiccup when a bad back landed him on the disabled list.
"I'm back to attacking the zone and staying aggressive," Vincent said. "For me, it's just getting strike one right now. And if they get out first pitch like they've been doing, it makes baseball a little easier."
Diaz gave up four singles and the lead in the ninth, but he still owns a 2.61 ERA and 82 strikeouts in 46 1/3 innings as a rookie.
"It's not easy to put that many hits together against Eddie Diaz," Servais said. "He has been really, really good. They did it and I give them credit. The middle of their lineup is very tough, but to Diaz's credit, he hung in there.
"I think that's a little bit of the [former] starter in him. As young players, sometimes relievers, when it goes awry like that, they can lose perspective on things, But he kept them right there and gave us a chance. Even though it wasn't his night, he kept us in the game and then we got the big home run late."
And his team closed this one out.
"That was a big win for us," Vincent said. "Toronto and Baltimore have to play each other. Detroit's got to play Cleveland. So this is a big three days for the AL Wild Card for everybody. Hopefully this starts us on a hot streak and we can keep rolling."