MINNEAPOLIS Martin Maldonado had one career at bat in the major leagues when he stepped to the plate on May 29.One. A couple swings, a couple looks and a pinch-hit strikeout.That was what the Brewers knew of Maldonado in the majors. But there he was, one half of their new catching tandem after Jonathan Lucroy broke his hand in late May.Since then, the rookie has hit .262, with four home runs in 42 at bats. They've been big home runs, too, and each has chipped away at a deficit or given the Brewers a lead. Perhaps none was more clutch than Friday night's two-run ninth inning blast that won the game for the Brewers, 5-3. "It was hammered," Ron Roenicke said. "Oh, it was hammered."The Brewers are hardly surprised. Why would they be?"You just don't know," Roenicke said of his expectations for the catcher. "When a guy comes to the big leagues, you don't know what's going to happen, and he had a very good year last year offensively in Triple-A, which was his first full season playing everyday. And he's fabulous defensively. He's got some huge hits in some key moments for us."Maldonado's first home run came in a 6-5 loss against Pittsburgh on June 3, but the past three have all been in wins, two against the Padres and this last one against the Twins. His .262 average is better than George Kottaras' .233 through Friday, and he already has more home runs and RBI than his counterpart. Maldonado has been a pleasant surprise in an injury-ridden season, and his offense has at times overshadowed the stellar defense the Brewers' staff was expecting from him.Maldonado has caught 111.2 inning so far this season. It's not a huge sample size, fewer even than Kottaras' 142, but he's been effective. He's thrown out two of the six runners who have attempted to steal with him behind the plate; if he'd caught enough innings to qualify for a statistical leaderboard, that mark would tie him with Yadier Molina and A.J. Ellis for fourth-best in the majors.What might be more impressive, though, is the infrequency with which runners dare to attempt to swipe a base on the rookie. Through Friday, they'd attempted to steal on him once every 27.9 innings. They've run on Kottaras once every 8.9 innings, on Lucroy once every 7.5. Maldonado's defense has been so sharp that after less than a month in the big leagues, Roenicke can joke about it."Now we just need to get him to be able to play good defense," Roenicke said.No one's going to interpret that as anything other than sarcasm.In fact, Roenicke, who served as a third base coach for the Angels from 2000-2010, is comfortable tossing around some big names while talking about his rookie catcher. In his position in the American League, Roenicke often coached against Ivan Rodriguez, one of the greatest defensive catchers of his generation. Roenicke said that when facing Rodriguez in tandem with a slow pitcher, he'd tell his players to run.They would often refuse."They'd say, Pudge is catching,'" Roenicke said. "They wouldn't run. And he was that good that you really did, you stopped running."Maldonado isn't Pudge yet, of course. But he's mature, so far from wide-eyed, Roenicke said. It's easy to forget how new this is to him, and his emergence will make Lucroy's return and the team's corresponding roster moves more complicated in a good way.In a season of injuries and uncertainty, Maldonado's early impact can't be overlooked. If the rookie even halfway lives up to the comparisons he's already garnered this season, it'll be hard to dispute his success. Follow Joan Niesen on Twitter.