But after four perfect innings from his bullpen, he still managed to pick up the first eight-game winning streak from a Giants starter since Rick Reuschel won eight in a row in 1989.
Unlike in past seasons, when Cain has been among the league leaders in lack of run support and has somewhat struggled to earn wins, during his eight-game winning streak, Cain has gotten 46 runs of support, an average of 5.75 runs per game.
And given he didn't have his best stuff Monday after his 125-pitch outing last week, Giants manager Bruce Bochy said he was just as impressed with the win against the Angels as he was with the perfect game.
"I'd say gutty effort. He wasn't quite on, which is not surprising with everything he put into last game," Bochy said. "He worked pretty hard in that game. He found a way to get it done. He just keeps grinding."
The win was the Giants' first in three games and just their second in the last five. With the Dodgers idle, the Giants (38-30) cut their deficit in the National League West to 4 1/2 games.
And though Cain didn't have the same stuff he had in his perfect game, he really didn't need to -- his bullpen had it instead.
After Cain departed following the fifth without a single perfect inning, the Giants' bullpen combination of Shane Loux, Sergio Romo, Jeremy Affeldt and Santiago Casilla, who earned his 19th save, combined to close out the game with four perfect innings.
"I was pumped by those guys. They were able to come in and finish off the game for me," Cain said. "They got 1-2-3 innings and I wasn't able to do that for some reason."
Before Monday night's game, Giants relievers had given up three runs in their last 5 1/3 innings. And when it looked like the bullpen was in for a long night after Cain left after just five, relievers efficiently ended the game with just 44 pitches over the final four innings.
"For those guys to come in and make quick outs was good and very helpful for those guys down the road and the rest of the series," Cain said. "Because it's usually never good when the starter comes out after five and those guys have to come in and pick you up."
With the game tied at 2 after Cain had surrendered a run in each of the first two innings, the Giants took the lead in the third inning when they strung together three straight hits against Angels starter Jerome Williams. After Melky Cabrera and Buster Posey singled with one out, Angel Pagan hit an RBI single to give the Giants a lead they would never give up.
Williams (6-5) lasted just 3 1/3 innings for the Angels (36-32), his shortest outing since his first start of the season, giving up four runs on seven hits while walking three.
The Giants would add insurance runs in the fourth and sixth innings on RBI singles from Ryan Theriot, who was 3-for-5 on the night.
The five runs the Giants scored were the most since they put up 10 on the Astros in Cain's perfect game last week. And it wasn't just the top of the order that was producing for the Giants, either, as the bottom third of the order was 5-for-10 with two walks, including three runs.
First baseman Brandon Belt was 2-for-2 with two walks from the seven spot, extended his hitting streak to a career-best seven games. During the streak, he is batting .455 with two doubles and three home runs.
"He's really settling in nice, having some good at-bats, using the whole field," Bochy said. "He made some adjustments, you can tell. Knowing he's in the lineup, I'm sure has helped."