This effort could help expedite that decision.
Wells cruised through six innings after giving up singles to the first two batters of the game, with Emmanuel Burriss stealing second and scoring on Mike Fontenot's single. He struck out seven against a lineup that featured Pablo Sandoval, Pat Burrell and Aaron Rowand, and didn't walk a batter.
The 6-foot-5 right-hander has a 1.35 ERA in 20 spring innings after going 8-14 with a 4.26 ERA in 32 starts for the Cubs in 2010.
"Confidence is a huge thing," he said. "I lost it last year and it is a tough thing to overcome. If you don't have confidence, even if your stuff is working, it is hard to get people out. I don't think confidence comes with getting guys out or having a good outing. It is about believing in yourself and knowing that you belong."
Wells also is taking the slow process involving the rotation in stride.
"It's not up to me and until a decision is made I can't really say anything," he said. "I've been goofing around and saying stupid comments, but it is just because I don't know what to say."
Cubs shortstop Starlin Castro, who turns 21 on Thursday, went 1 for 3 and is batting .383 this spring with a team-best four homers and 12 RBIs.
"It's just spring training and I am working on things, but I am feeling confident," said Castro, who also committed an error against the Giants. "I know I am not starting in minor leagues and I can help us, hopefully, get into the playoffs."
Cubs manager Mike Quade likes what he has seen from Castro, who batted .300 with 41 RBIs last season as a rookie.
"He looks like he's driving the ball better, and yes, it's Arizona," Quade said. "I don't know and I don't care, I'm happy with it. He's growing up physically and mentally and you've got to like what you see."
The Cubs won it on Wellington Castillo's one-out RBI single off Josh Banks.
Shane Loux started for the Giants and allowed a run and two hits in 3 2/3 innings.
Cubs 3B Aramis Ramirez had temperature of 102 degrees on Saturday and although it was slightly better Sunday, Ramirez was replaced in the original lineup by Josh Vitters. ... Cubs LHP John Grabow made his third appearance, a scoreless seventh, after dealing with shoulder tightness early in camp.