The win gave the Saguaros a 25-10 (.714) record with two games -- including Saturday's AFL Championship Game against Salt River -- remaining. The best winning percentage in league history is .705 (31-13), set by Mesa in 1999. Surprise needs to win both games to surpass that mark.
Seratelli, who played first base, second base and the outfield while hitting .282 and stealing 35 bases for Double-A Northwest Arkansas this season, manned first against the Solar Sox on Wednesday. Entering the game, just two of his 19 AFL hits had gone for extra bases -- one homer and one double.
Facing right-hander Terry Doyle (White Sox), who came into the game with a 4-0 record and 1.85 ERA in seven AFL starts, the switch-hitting Seratelli sent a 2-0 fastball over the right-field wall to give the Saguaros an early lead.
That was the only hit Doyle allowed over three innings. The Solar Sox starter struck out four, walked one and finished his fall campaign with a .135 average against in 27 1/3 frames.
Mesa struck back against Surprise reliever Billy Bullock (Braves) in the fifth. A single and a pair of walks loaded the bases with no outs. After Bullock fanned Xavier Avery (Orioles), White Sox prospect Tyler Saladino smacked an 0-1 slider into center field to give the Solar Sox a 2-1 advantage.
The Saguaros answered in the sixth as Todd Cunningham (Braves) walked, stole second, went to third on a wild pitch and scored on a single by former No. 1 Draft pick Tim Beckham (Rays). Two more singles by Wil Myers (Royals) and Leonys Martin (Rangers) plated a third Surprise run that proved to be the game-winner.
Surprise had just five hits in the game -- three of them in the two-run sixth. Seratelli's blast was the only extra-base hit of the afternoon for either club, as Mesa was limited to six singles. Cubs prospect DJ LeMahieu collected two of them.
Mesa's Nevin Griffith (White Sox) fell to 0-2 after yielding two runs on three hits and a walk in the sixth. He struck out one and saw his ERA rise to 9.64 in 13 AFL outings.
Left-handed reliever Adam Liberatore (Rays) improved to 2-0 with 1 2/3 perfect innings. He took over from Bullock with two on and one out in the fifth, struck out the next two batters, then got three consecutive groundouts in the sixth.
Rangers relief prospect Johan Yan induced three straight groundouts in the ninth to notch his second save.
The AFL's regular season concludes Thursday afternoon with Surprise traveling to Salt River in a preview of Saturday's championship and Mesa hosting Scottsdale. The games, along with the Phoenix-Peoria matchup, begin at 12:35 p.m. MT and are scheduled to go seven innings.
John Parker is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.