Villanueva surrendered 11 hits and five runs over five innings as the Brewers beat the Cubs 5-2, giving the beleaguered Chicago hurler his fifth loss on the season in six decisions.
"I want to help the best that I can here," he said. "Obviously, when I am not giving the (team) the best chance to win it is a little frustrating."
Despite yet another rocky outing, Villanueva actually lowered his ERA to 10.42 from 10.93.
"I felt at times in good rhythm. I didn't feel I was getting behind too much. A bleeder here, a bleeder there. That has been the story so far for me personally," Villanueva said.
Matt Garza pitched seven strong innings and Lyle Overbay hit his first homer this season for Milwaukee. Carlos Gomez and Ryan Braun each had three hits and a stolen base for the Brewers, who have a Major League best 17-6 record.
Garza (1-2), who pitched part of last season with the Chicago, retired the Cubs in order in four of the first six innings. He gave up two runs and four hits while striking out seven and walking one.
Francisco Rodriguez pitched a scoreless inning to pick up his 10th save in 10 chances.
The Brewers scored in the first when Cubs left fielder Junior Lake appeared set to make a routine catch of Scooter Gennett's line drive but the ball sailed past Lake's glove and rolled to the fence, allowing Gomez to score.
Braun's single drove in Gennett, who scored as Lake airmailed a throw to the plate, giving the Brewers a 2-0 lead.
"The first inning obviously didn't start off well," Cubs manager Rick Renteria said. "We had the fly ball that Junior (Lake) kind of misplayed. Not a very clean first inning, which put (Villanueva) in a position to have to work in quite a few more pitches."
Villanueva said Lake apologized to him between innings.
"I know he is not trying to make a mistake. You can see the frustration in him," Villanueva said. "If he didn't care then he would be getting a different type of chat from me."
The Cubs cut the lead to 2-1 in the third on Emilio Bonifacio's run-scoring single.
The Brewers extended their lead to two runs again in the bottom half of the inning. With Gomez on first, Braun hit a ground ball deep in the hole at short. Cubs' shortstop Starlin Castro made a strong throw and umpires initially ruled Braun out at first. After a delay of two minutes and 20 seconds, Braun was ruled safe. Jonathan Lucroy followed with a single to score Gomez.
Overbay led off the fourth with a homer, giving the Brewers a 4-1 lead. Aramis Ramirez's sacrifice fly in the fifth extended the lead to 5-1.
Ryan Sweeney's ground-out plated a run for the Cubs in the seventh.
Garza insisted facing the Cubs, for whom he pitched in 2011 and 2012, as well as part of last season, didn't generate any added emotion for him.
"I've been on five different teams. If I had to get up for everybody, I'd be tired by midseason," Garza said.
Asked if he sensed the frustration of his former teammates, who sit in last in the National League Central, Garza responded: "I don't care. I'm worried about my 25 guys in this locker room."
Notes: The Brewers unveiled a statue of Hall of Fame radio announcer Bob Uecker, situated in the last row of the upper deck behind home plate, that pays tribute to the classic Miller Lite ad campaign in which he starred. .. Rodriguez tied Robb Nen for 18th place with his 314th career save. .. Chicago reliever Neil Ramirez pitched a scoreless inning in his Major League debut. It is everything you dream about as a kid, the first time on a big league mound," Ramirez said. "I was just happy to keep it under control and keep the team in the game." .. The Brewers' Marco Estrada (1-1) will face the Cubs' Travis Wood (1-2) on Saturday.