Villanueva threw six scoreless innings in the Cubs' 4-1 victory over the Milwaukee Brewers on Friday.
"I had that one walk and I'm furious about it," he said. "I hate giving up those free runners. I don't know what the percentage is but they almost always score. It sounds weird but I'd almost rather give up a home run than a walk because if they're going to score, at least they're going to earn it."
No one scored against Villanueva, who allowed five singles and struck out four in his best outing of the spring. The right-hander, who signed a $10 million, two-year contract with the Cubs in the offseason, had allowed eight runs and 15 hits in 11 2/3 innings across his four prior starts.
Villanueva, who was 13-11 in two seasons as a part-time starter in Toronto, is slated for the last spot in what he believes is a vastly improved rotation for Chicago.
"I think it's a good mix of veteran guys who have been around a couple teams now so we know how it is," Villanueva said. "We may not have all the aces but we have a rotation that will keep us around games. Hopefully, one of us turns into that other ace or couple aces that we need."
Villanueva also helped the Cubs score their only run against Brewers starter Yovani Gallardo in the fifth. Luis Valbuena moved to second on Villanueva's sacrifice and scored when Donnie Murphy failed to make a sliding, backhand catch of a high pop fly to shallow left field for an error.
Gallardo yielded the unearned run and four hits in 5 1/3 innings. He has one spring outing left before taking the mound for his fourth straight opening-day start.
"They stay the same," Gallardo said. "It's opening day. We're all excited and ready to get started. Fans are excited and there's that extra adrenaline that first game. Just got to find a way to stay relaxed and pitch like it's any other game."
Barney belted a two-run shot before Navarro connected against Michael Olmsted to give the Cubs a 4-1 lead.
Despite his offensive numbers, Brewers manager Ron Roenicke said Davis remains on the bubble for making the roster. ... David DeJesus and Starlin Castro each had two hits for the Cubs. ... The Cubs sent 11 players to minor league camp -- pitchers Drew Carpenter, Jaye Chapman, Casey Coleman, Jensen Lewis, Blake Parker and Chris Rusin, infielders Edwin Maysonet and Brad Nelson, and outfielders Brian Bogusevic, Johermyn Chavez and Darnell McDonald. ... RHP Marco Estrada, who has a sparkling 0.96 ERA for Milwaukee, starts Saturday against the Los Angeles Angels.