Pagan did his part, but the rest of the Giants mustered six singles off Brewers starter Wily Peralta and three relievers. The outcome extended right-hander Jake Peavy's personal losing streak to 12 consecutive decisions.
The Giants, who dropped two of three games to the Brewers, missed a chance to win their first series against an above-.500 team since they took three of four from St. Louis from May 29-June 1.
Perhaps Pagan, the switch-hitting center fielder who missed 44 games with a strained back, will give the Giants the lift they need to compete more effectively and accelerate their pursuit of the first-place Dodgers in the National League West.
"The good thing is, we're still in the fight," he said. "This is the time for us to get on a roll and finish strong."
Pagan, 33, felt confident that he can remain healthy for the regular season's final seven weeks. "I'm very positive everything's going to be fine," he said. "... My goal is to stay healthy and [help] this team win another championship."
Pagan's availability has been an issue since last year, when a hamstring injury limited him to 71 games. The Giants fully realize that they need him on the field, as reflected by their 36-22 record this year in games he has started.
"He's a bona fide leadoff hitter," Peavy said. "With power lacking in the game overall, speed is more important. He brings some energy to the ballclub. ... [He] makes us a whole lot better team."
Appearing in his first Major League game since June 14, Pagan didn't make authoritative contact at the plate. Yet he executed his tasks as a leadoff hitter and offensive dynamo nevertheless.
"I thought he bounced around nicely and didn't show any signs of his back bothering him," Giants manager Bruce Bochy said of Pagan.
Pagan opened the game with a bloop single to right field off Peralta (14-6), the Majors' leading winner. The Giants proceeded to load the bases with two outs before Joe Panik became the first of Peralta's nine strikeout victims.
After Peavy reached base safely by striking out on a wild pitch to begin the Giants' fifth, Pagan bounced a single into right field. Hunter Pence scored Peavy with a single to center, but Peralta recovered by striking out Buster Posey and coaxing Pablo Sandoval's double-play grounder.
"That's a situation where you have to calm down and make your pitches," Peralta said. "I was able to do that today. Posey and Sandoval, those are two great hitters."
That run erased the 1-0 lead Milwaukee established in the first inning on Ryan Braun's RBI double.
The Brewers scored twice off Peavy in the sixth. Aramis Ramirez doubled and came home on Khris Davis' ground-rule double. Rickie Weeks' single set up Mark Reynolds' sacrifice fly that delivered Davis.
Peavy's lapses during the third time through the batting order have marred each of his three starts with the Giants since they obtained him from Boston. The Dodgers scored three fifth-inning runs off him in his San Francisco debut on July 27. Last Saturday, the Mets raked him for four seventh-inning runs after he retired the first 19 hitters he faced.
"I've got to do more," Peavy said. This entails making better pitches in crucial situations, because, he added, "I can't give any more than I've given."
Pagan also felt ready to do all he can.
"My teammates need me," he said.