The Brewers prospect hit for the cycle, going 5-for-5 with eight RBIs and three runs scored in an 18-3 romp over the AZL Indians.
"It was tremendous, you don't have a game like that without being locked in," Brewers manager Tony Diggs said. "He was just on tonight. He hasn't had much playing time, but he made the most of it tonight."
Mejia actually didn't start the first game of Friday's doubleheader, instead replacing Tyrone Taylor as the Brewers' designated hitter in the bottom of the second inning. Before he could begin his offensive assault, Dionis Hinojosa was picked off and thrown out at second.
Leading off the third, however, Mejia took care of the home run first, taking Anderson Polanco deep to center field. The 22-year-old singled in the fourth and hit a three-run double in the fifth. He cleared the bases again and completed the cycle with a triple in the seventh before adding a single in the eighth for good measure.
"As soon as he hit the ball, [the guys in the dugout] were all standing up, jumping around, hoping he'd at least try to make the triple, because it was a ball in the gap," Diggs said. "I think he had it in his mind he was going to go for it regardless and he beat that throw to third base, had a nice little celebration."
It was just the fourth appearance of the season for the native of the Dominican Republic. And he'd had only four at-bats prior to Friday's historic outburst.
This season is Mejia's first in the United States. He signed with the Rockies as an international free agent in 2008 and spent the following season in the Dominican Summer League, hitting .227 with three homers, 16 RBIs and a .333 on-base percentage in 39 games.
Released by Colorado in May 2010, Mejia joined the Brewers a couple of months later. He appeared in 14 games for the DSL Brewers that year and returned to the team last season, where he played catcher and hit .313 with a .377 OBP and .441 slugging percentage in 56 games. He slugged three homers and drove in 37 runs to earn him a spot on the DSL All-Star team.
Mejia went 0-for-3 in Friday's nightcap, with hard-hit balls in each at-bat, Diggs said. That left him 6-for-12 with nine RBIs in five games.
"He kept it going in the next game, too. It's a proving point for a guy that's not getting much playing time when he comes in and produces like that," Diggs added. "It's something that he can stand on and say, 'Give me a chance.'"