Jeremy Slayden did his best to stay calm in the dugout for eight innings, watching his teammates struggle for a shot to play in the championship game.

"You could feel the tension in the air," Mesa Solar Sox manager Rocket Wheeler said. "It was a close ballgame, and I told Jeremy, 'Get a bat, start thinking about hitting.' And sure enough, he came in with the bases loaded."

Slayden stepped to the plate in the eighth, took a few pitches and -- just as Wheeler drew it up -- slugged a pinch-hit, go-ahead grand slam on a 1-2 pitch en route to the Solar Sox's 7-4 win Wednesday to seal a spot in the Arizona Fall League championship game.

"I told him to be ready, there's a chance to pinch hit," said Wheeler. "And he came through big."

Slayden's slam was the difference in the tiebreaker to determine who would advance to Saturday's title contest against the Phoenix Desert Dogs.

"It felt great," Slayden said. "The main thing was to stay calm. I hadn't had any swings up to that point, so I wanted to stay loose and get ready."

Mets prospect Eddie Kunz was on the mound, a right-hander who worked his way up from Double-A to Shea this summer.

"I took a jog, grabbed my bat, took a couple swings and sure enough, we got some guys on, got the bases loaded and [Wheeler] pointed to me and said, 'Hey, you're in,'" Slayden said. "I took a couple practice swings, stepped into the box and the first pitch he threw one right down the middle. It was a great pitch to hit and I was kind of worried I'd taken it. I fouled off another for an 0-2 count and I knew I had to see the ball up."

Kunz, fresh off a scoreless outing against Scottsdale on Saturday, tried to lure Slayden out of the strike zone with a ball in the dirt and end the threat.

"He threw a slider, but I laid off it. The next pitch, it was a fastball down the middle, and I wasn't trying to do too much with it," Slayden said. "I just got the barrel on the ball."

Slayden's third home run landed deep over the right-center field wall, setting a date with the Desert Dogs this weekend.

"This has been a blast for me, no pun intended," Wheeler laughed. "This group of kids ... they come together, they have fun, they have a good time. That's all I ask -- hit the ball, run hard, play your defense hard -- and that's what they've done."

Mesa leads the fall league in batting average (.329), homers (51), RBIs (284) total bases (713), runs (303), hits (436) and slugging percentage (.539). "Everyone has done so well," said Slayden, who is batting .300 with 27 RBIs in 25 games. "I've had an OK fall, but I haven't played as well as I wanted to. I was telling myself, I need to change it right here. It was a nice feeling to do that for the team."

"These kids have been loose and played hard all fall, and I tip my hat off to them," Wheeler added.

Mesa (26-11) and Peoria (25-12) had split their six games this season coming into Wednesday's win-and-clinch tiebreaker.

"We all knew this was the biggest game of the fall," said Slayden, a Georgia Tech product who spent the summer with Double-A Reading. "We felt they'd been our best competition all year. We knew it was going to be a fun game. I knew I wasn't going to play, but I went in early and hit some BP with [hitting coach] Ryne Sandberg. I knew I could get in today."

Wheeler said he'd written up his lineup last week and left Slayden out of it. The pinch-hit appearance was somewhat planned, however.

"We mentally prepared for this, we were ready to win," Slayden said. "As far as extra pressure, I think we've been relaxed the whole season."

Wheeler, who managed the Class A Advanced Myrtle Beach Pelicans to a division title in the regular season, said his team understood the task.

"I think you could feel a little pressure, the intensity of the game -- there's something about every play," he said. "They went out got the job done, they did a good job.

Cubs starter Jesse Estrada allowed four runs on five hits and a pair of walks over four innings for Mesa. Aaron Thompson (Marlins) hurled a pair of scoreless innings before Braves reliever Kris Medlen (1-1) struck out five over three perfect frames for the win.

"Estrada held them, Thompson came in and did his job and Medlen closed it out, so it was a good afternoon," said Wheeler.

Peoria took an early lead when Cardinals prospect Brett Wallace slugged his sixth homer in the first. Nationals farmhand Bill Rhinehart added a two-run homer in the third and Shane Robinson (Cardinals) capped the frame with a sacrifice fly.

Jeff Larish (Tigers) homered in the second, and the Solar Sox added a couple more in the third as Tyler Flowers hit an RBI single and Logan Morrison scored on fellow Marlins prospect Scott Cousins' double play.

Cardinals reliever Justin Fiske (0-2) was charged with two runs on one hit and a walk to suffer the loss. He did not record an out.

Mesa will hand the ball over to the fall league's hottest pitcher, Braves hurler Tommy Hanson (5-0, 0.63), in the championship game Saturday morning.

"He's had a heck of a fall league here, he's pitched extremely well," Wheeler said.

"We have a whole lot of confidence, especially in him," Slayden said. "He's done a great job for us every game. We've put up some serious runs this fall and we feel good about it."