SAN FRANCISCO -- On a night when his opponent was at his best, Tyler Chatwood was even better Wednesday night.

That was not really a surprise, being that the Colorado Rockies right-hander was on the road.

Chatwood continued his brilliant pitching away from Coors Field, limiting the San Francisco Giants to three hits over eight shutout innings in the Rockies' 2-0 victory.

Nolan Arenado and Gerardo Parra drove in runs against hard-luck loser Jeff Samardzija as the Rockies snapped a five-game losing streak while denying the Giants an opportunity to improve upon their chances of landing a National League wild-card spot.

"Let's not take anything away from that kid," Samardzija said. "He pitched a great game."

The Giants (83-75) fell 1 1/2 games behind the New York Mets (85-74) in the chase for the top wild-card spot with just four days remaining in the regular season. However, San Francisco retained a one-game advantage over the St. Louis Cardinals (82-76) for the final postseason berth.

The loss came after the Giants saw the Cardinals' 2-1 loss to the Cincinnati Reds flash on the scoreboard.

"You'd like to take advantage of the situation when the other team loses," Giants manager Bruce Bochy said, "but they're probably saying the same thing."

Chatwood improved his road record to 8-1 and lowered his road ERA to a franchise-record 1.69 with his fourth combined shutout of the season. He struck out nine and walked two.

"I'm very happy and proud of myself for what I was able to overcome," said Chatwood, who underwent two elbow surgeries in the past two years. "Just to be able to finish on that note is awesome."

Left-hander Boone Logan served up a double to pinch hitter Kelby Tomlinson to lead off the ninth, then struck out the next two batters he faced, pinch hitter Gorkys Hernandez and Denard Span.

However, Logan failed to cover first base in a timely manner on Brandon Belt's grounder to first baseman Parra that could have ended the game, allowing Belt to reach safely and putting the potential tying run on base.

Right-hander Adam Ottavino then took over and got Buster Posey to ground out to third base on a full count for his sixth save.

Chatwood's .889 road winning percentage is tied with the marks of the Los Angeles Dodgers' Rich Hill, the Washington Nationals' Stephen Strasburg and the Toronto Blue Jays' Aaron Sanchez for the best in baseball.

The 1.69 road ERA is the lowest in the majors, followed by Hill's 1.74.

"He made it interesting with a couple of leadoff walks late, but he gets the ground ball and that's what he's really good at," Rockies manager Walt Weiss said of Chatwood. "To shut that team down for eight innings, that was impressive."

Chatwood (12-9) allowed leadoff singles to Span, Hunter Pence and Conor Gillaspie in the first three innings, but only two other baserunners -- walks to Belt and Brandon Crawford, both of which were followed immediately by double-play grounders -- before being lifted for a pinch hitter in the top of the ninth.

Chatwood outdueled Samardzija (12-11), who struck out a season-best 11 in six innings.

"Two different teams," Bochy said of his squad, which erupted for 19 hits in a 12-3 win in the series opener Tuesday. "We just couldn't figure (Chatwood) out."

The Rockies got seven hits off Samardzija, including two apiece in the fourth and seventh innings to produce the game's only scoring.

Samardzija, who walked just one, was pulled after allowing a double to David Dahl and an RBI single to Parra at the start of the seventh as Colorado expanded the lead to 2-0.

The double-digit strikeout effort was the ninth of Samardzija's career.

"Tale of three seasons for me," the first-year Giant said. "Good start, lull in the middle, and good at the end. I really like the way I'm finishing the season."

The Rockies loaded the bases against the San Francisco bullpen in the eighth, but Hunter Strickland kept the Giants within arm's length by getting Parra to fly out to right field.

Carlos Gonzalez had three hits, including a double, and Charlie Blackmon added two hits for the Rockies, who had lost 18 of their previous 23 road games.

Colorado out-hit San Francisco 9-5.

The Giants were shut out for the 13th time this season, the ninth time since the All-Star break.

Samardzija struck out 10 of the first 18 batters he faced, but back-to-back hits put him in a 1-0 hole in the fourth inning.

Actually, it almost took just one hit to do the damage, as Gonzalez missed a home run by about a foot with a blast off the left field wall with one out.

Arenado followed with a broken-bat blooper to center, a single that produced his 130th RBI when Gonzalez scampered home.

The Giants had two of their first four baserunners erased on stolen-base attempts. It marked the first time Rockies catcher Tony Wolters threw out two potential base-stealers in the same game this season.

NOTES: The Rockies had lost eight straight on the road. ... The previous Collorado record for season road ERA was 2.44 set by RHP Jhoulys Chacin in 2013. ... 3B Nolan Arenado joined 1B Andres Galarraga and 1B Todd Helton as the only Colorado hitters to have multiple 40-homer/130-RBI seasons. ... Rockies manager Walt Weiss kept 2B DJ LeMahieu, the National League's leading hitter, out of the game and said he would continue to do so if it meant protecting his advantage over Washington Nationals 2B Daniel Murphy. ... Former Giants 3B Matt Duffy visited the San Francisco clubhouse before the game to pick up belongings left behind when he was dealt to the Tampa Bay Rays at the trade deadline. Duffy has been in Southern California rehabbing after heel surgery.