Buster Posey scored on Cody Bellinger's throwing error to break an eighth-inning tie Tuesday night and lift the San Francisco Giants to a 2-1 victory over the visiting Los Angeles Dodgers in the opener of a three-game showdown series between the top two teams in the National League West.

Right-hander Logan Webb combined with three relievers on a six-hitter as the Giants (63-37) stretched their lead over the second place Dodgers (61-41) to three games.

With the score tied at 1-1, Posey and Mike Yastrzemski drew consecutive walks from the fourth Dodgers pitcher, Blake Treinen (2-5), to lead off the eighth.

Darin Ruf grounded out to second baseman Max Muncy, but Bellinger, the first baseman, threw the ball away trying to get Posey rounding third base. That allowed the Giants' catcher to jog home.

Tyler Rogers (2-1), who pitched out of a second-and-third, one-out jam in the top of the eighth, was credited with the win. Giants closer Jake McGee worked a 1-2-3 ninth for his 21st save.

The tight win was the Giants' third straight over the Dodgers. San Francisco rallied from behind in the ninth inning on consecutive nights for 4-2 and 5-3 victories to wrap up a 3-1 series win in Los Angeles last week.

Both starting pitchers, Webb and Dodgers left-hander Julio Urias, left a 1-1 tie in the sixth inning Tuesday, and neither got a decision.

Webb took a no-hitter into the fifth before allowing a leadoff single to Bellinger, who came around to score the game's first run on a one-out single by Billy McKinney.

Webb left for a pinch hitter in the last of the sixth, trailing 1-0 at that point. He limited the Dodgers to just the one run and three hits in six innings, walking one and striking out five.

The Giants tied the score against Urias in the sixth on a double by Austin Slater and a single by Posey.

Urias was pulled two batters later, charged with one run on six hits in 5 2/3 innings. He struck out five and did not walk anyone.

Posey had two hits for the Giants, who evened the season series at 7-7 with five games remaining. All five of those games will be played in San Francisco, including three in September.

A.J. Pollock and Chris Taylor had doubles for the Dodgers, who had entered the series on a two-game winning streak.

--Field Level Media