The weekend series featured one-run margins, with the Dodgers dropping two of the three games to fall five games behind San Francisco in the National League West.
Urias was on the same pitch limit as his other three starts, roughly 90 pitches, and this time he made it last into the sixth inning for the first time. Urias struck out seven for his second straight start, and kept the Giants off the board through five innings.
With the top of the Giants' lineup due up in the sixth inning and Urias sitting at only 77 pitches he remained in the game. But after a one-out single by Joe Panik, Brandon Belt smashed a slider left over the plate over the wall in right center field for a 2-0 Giants lead.
The final pitch to Belt with the 86th of the night for Urias, who was 86'd by the home run.
The Dodgers were still stuck and zero because they couldn't score off Jake Peavy, on a limit of his own and at the other end of the spectrum of his career relative to Urias. Peavy, who entered play with a 6.41 ERA, threw six scoreless innings in his 369th career start and reached 90 pitches for just the fifth time all season.
Only after Peavy left the game were the Dodgers able to score, in the form of a splash home run by Joc Pederson off Hunter Strickland in the seventh inning.
It was the culmination of a dark week for the Dodgers offense, which scored 13 runs and totaled 32 hits in six games and lost four of the six contests, all within the division.
The Dodgers have lost five of seven games at AT&T Park in 2016.
The road trip moves on to Chase Field Arizona, a hitter-friendly park as if that term seems capable of use by this Dodgers offense. Old friend Zack Greinke gets a chance to carve up his old team in the series opener on Monday night, while Mike Bolsinger will try to go six innings for the first time since 2015.
Home runs: Joc Pederson (9); Brandon Belt (8)
WP - Jake Peavy (3-6): 6 IP, 4 hits, 1 walk, 3 strikeouts
LP - Julio Urias (0-2): 5⅓ IP, 4 hits, 2 runs, 1 walk, 7 strikeouts
Sv - Santiago Casilla (13): 2 up, 2 down