Career win No. 50 fell out of Kennedy's grasp for the eighth consecutive start, though he was more effective Friday than he has been recently, after a laborious first inning.
The Giants plated two runs and forced Kennedy to throw 28 pitches in the first as San Francisco claimed an early 2-0 advantage. Gregor Blanco came around to score from first on Buster Posey's double off the left-center-field wall. Didi Gregorius' relay beat Blanco home, but catcher Miguel Montero couldn't catch the ball to apply the tag.
"Buster got a key hit," Giants shortstop Brandon Crawford said. "Hunter [Pence] had a key hit. Otherwise, [Kennedy] looked like the same guy."
Posey scored on Pence's single later in the inning to give the Giants their second run.
"I think he came out and tried to establish his fastball early, and they were aggressive and got some hits on him and got a couple runs out of it," D-backs manager Kirk Gibson said. "They put some pressure on him, but he made some pitches after that and got out of it and started pitching much better. He got his arm up and had a good outing -- six innings, two runs."
Kennedy did not overpower the Giants, but he was efficient after the first inning. He lasted six innings and retired 11 of the final 12 batters he faced.
"I just made little adjustments here and there," Kennedy said. "I'm not sure if it was being off for four days [that led to the early trouble]."
Kennedy pointed to a changeup he threw to strike out Giants first baseman Brandon Belt in the third inning as when he felt in command.
"That was one of the better changeups I've thrown," Kennedy said. "I threw a bad one over to Posey and he fouled it off. I said, 'OK, that's one you don't want to throw.'"
Kennedy's turnaround went for naught as the D-backs' offense remained silent throughout the evening against Giants starter Chad Gaudin, who tossed seven stellar innings and now has a 2.23 ERA in seven starts since moving to the rotation and stretched his scoreless-innings streak to 11. It was just the second time this season that Arizona has been shut out.
"We didn't have any offense going on tonight, and they just shut us down," Gibson said. "I think you have to give [Gaudin] some credit. He was throwing the ball well to both sides of the plate."
Even Paul Goldschmidt, who entered the game with eight home runs and 28 RBIs against San Francisco since 2011 -- both Major League-bests -- went hitless Friday.
The only time Arizona threatened to score was against the San Francisco bullpen in the eighth. A.J. Pollock and Adam Eaton both singled and Aaron Hill walked, but the recently activated Santiago Casilla induced a forceout off the bat of Goldschmidt to end the inning.
"It was the only opportunity we had with Goldy up there with the bases loaded," Gibson said. "He hit the ball solid but right to the shortstop and we didn't get it done."
With a struggling rotation outside of Patrick Corbin for much of the first half, the D-backs could certainly use a revived Kennedy to hold off the rest of the division. Although his numbers are subpar -- 3-7 with a 5.29 ERA -- he has recorded a quality outing in four of his past seven starts.
"I think that's what separates the best pitchers in the game, is making adjustments, and I did that tonight," he said. "The fastballs were better by the third inning. I was getting ground balls. It allowed me to work better with offspeed pitches."
With the loss, the D-backs' lead in the National League West shrunk to 1 1/2 games over the Dodgers, and the Giants moved to within 5 1/2 games.