Molina hit a two-run homer, Joe Kelly threw six scoreless innings and St. Louis beat Chicago 4-0 Saturday.
Molina also had a double in his second game since coming off the disabled list Thursday from a sprained right knee.
"Today, I feel comfortable," Molina said. "Everything went well."
Molina homered off Travis Wood for a 4-0 lead in the sixth after Matt Holliday was hit by a pitch. Molina's ninth homer was his first hit in eight at-bats since he came off the disabled list.
Cardinals manager Mike Matheny also liked how Molina made a strong throw after handling a tough bunt and how he guided Kelly.
"We're happy he's here," Matheny said.
Kelly (4-3) hasn't lost since joining the Cardinals rotation as the fifth starter on July 6. He allowed four hits, struck out six and walked three.
"He's stepped up and really taken advantage of it," Matheny said "You can tell he can't wait to get the ball. When he goes out there with that kind of confidence it kind of transfers over to everybody else.
And he's getting better.
"We're still real impressed with how he's using his secondary pitches in tough counts. He's staying out of the middle of the plate. He's making good pitches when he has to. He's working ahead, all the things we hope our starters will do."
Cubs shortstop Starlin Castro was pulled shortly after making a mental mistake that let the Cardinals score in the fifth.
The Cardinals led 1-0 and had the bases loaded with one out when Castro caught a popup by Matt Carpenter in short left field. Castro put his head down and hesitated to throw home. Jon Jay scored from third base and the other runners advanced.
"I think good teams constantly find ways to put pressure on the defense, and Jon is such a heads-up player," Matheny said. "He took two hard steps and saw he had an opportunity."
Cubs manager Dale Sveum said something to Castro when he reached the dugout. Donnie Murphy switched from third base to shortstop to replace Castro in the sixth, and Cody Ransom came off the bench to play third.
Sveum said there is no explanation for Castro's mistake. He was unsure if Castro would play Sunday.
"I know the outs and everything," Castro said. "I just put my head down, like a mental mistake. I don't want to say any excuse for that.
"It's my mistake and that's why I pay for that. That's why I got taken out of the game. I feel really, really bad that happened."
Wood (7-10) retired the first nine St. Louis batters. He gave up four runs and four hits in 5 1/3 innings.
Carpenter hit a leadoff double in the fourth and scored on a double by Carlos Beltran for a 1-0 lead.
A trio of St. Louis relievers combined to allow one hit. Both teams finished with five hits.
The Cubs have lost 14 of their last 19 games. They have been shut out in five of their last seven at Wrigley Field.
"You've got to give credit to Kelly. That's pretty overpowering stuff," Sveum said.
The Cardinals recalled LHP Tyler Lyons from Triple-A Memphis before the game. He is 2-4 with a 5.35 ERA in seven starts. LHP Sam Freeman was optioned to Memphis after pitching four scoreless innings Friday against the Cubs. ... Cubs RHP Edwin Jackson (7-12, 5.05 ERA) will face Cardinals RHP Adam Wainwright (13-7, 2.71) Sunday in the series finale.