Martin Maldonado has caught Wily Peralta dozens of times, going back to their days together rising through the Milwaukee Brewers' system.

Maldonado has seen the big right-hander at his best, and at his worst. But it's when Peralta has it all going on the mound that his friend/catcher considers how dominating the Brewers' top pitching prospect might be one day.

"Everybody knows he has a good fastball," Maldonado said. "He can throw 96-97 (mph) with that good sinker. But when the secondary pitches are there, the slider and changeup, he can be as good as anybody in this game right now."

The Brewers got glimpses of that potential greatness last September when Peralta was summoned from Class AAA Nashville. In his second start, he limited Atlanta to one run over six innings. Next time out against the New York Mets, Peralta was even better, allowing only two hits over eight shutout innings.

Peralta had a "hiccup" game in Washington in which he had trouble throwing strikes but bounced back with a strong outing in Cincinnati. He was blanking the division-leading Reds on two hits, with six strikeouts, into the sixth inning when he began experiencing biceps tightness and was removed.

That September showing (2-1, 2.25 ERA) prompted the Brewers to pencil the 23-year-old Peralta into their rotation for 2013. He will make his third start of the season Tuesday night against the defending world champion San Francisco Giants at Miller Park.

"We saw him really good at the end of last year," said Brewers pitching coach Rick Kranitz. "He was throwing all three pitches for strikes.

"He has something a lot of pitchers don't have and that's a tremendous power, sinking fastball. That's a pitch that hitters don't like to see. Sometimes, you don't have to throw anything else. It's what they call very 'heavy.'

"His secondary stuff is still a work in progress. We've seen them be very good and we've seen them a little inconsistent. But that's a young guy trying to do too much. He has to understand that he doesn't have to do too much to get hitters out. He can get guys out inside the strike zone with his stuff."