Haniger, the Brewers' No. 12 prospect, finished the game 2-for-4 with a double and two runs. He said he was happy to come up in such a key situation.
"It's definitely what you want, a good situation, bases loaded," Haniger said. "I was looking for a pitch to drive and got a good pitch to hit. It was a 3-1 fastball, middle-in."
Power has been a big part of Haniger's game since he was at Cal Poly. He hit 13 home runs in his junior year before the Brewers made him the 38th overall selection in the 2012 First-Year Player Draft. This season, he hit 11 home runs in 129 games between Class A Wisconsin and Class A Advanced Brevard County.
After finishing his first full professional season, Haniger said he wants to bring the same mindset he's had all year to the AFL.
"I'm just trying to keep everything simple, play the game I've played all year," Haniger said. "Just trying to hit the ball hard each at-bat and keep it simple."
Haniger also doubled and scored a run in Surprise's two-run first inning.
Left-hander Miguel Pena started the game for Surprise and threw three perfect innings before giving way to the Saguaros' bullpen.
Peoria had more success once Pena left the game and tied the game in the top of the sixth inning before Haniger's grand slam. But the Javelinas weren't done. Third baseman Cheslor Cuthbert, the Royals' No. 9 prospect, led off the seventh inning with a home run to right field.
After the Javelinas added two more runs in the eighth inning, catcher Austin Hedges, the Padres' No. 2 prospect, led off the ninth inning with a single. But right-hander Trey Haley retired the next three hitters to close out the victory and earn the save.
Center fielder Aaron Altherr, the Phillies' No. 18 prospect, went 2-for-3 with two RBIs to lead Peoria's offense.
After his Opening Day heroics led the Saguaros to a narrow victory, Haniger said he is settling into life in the AFL.
"It's pretty cool. Most of the guys are cool and I'm becoming more talkative and started to become friends with some guys," Haniger said. "And it's nice to know a few of the Brewers players before I came out here; I'm living with two of them, so it's been real fun. It's definitely different, but I'm really enjoying it."