DENVER -- Their offense was again marginal Tuesday night, but the San Francisco Giants parlayed a strong start, spotless relief pitching and, most of all, an unearned run in the ninth inning to beat the Colorado Rockies 3-2.

The Giants mustered eight hits -- seven singles and Eduardo Nunez's home run in the third -- an output that was robust in the wake of their recent struggles. They tied the game in the eighth on a groundout and won it in the ninth, largely because of a throwing error by Colorado shortstop Daniel Descalso.

Buster Posey, leading off the ninth, reached second base when Descalso fielded his routine grounder and threw the ball over first baseman Gerardo Parra.

"I just didn't make a good throw at a bad time in the game," Descalso said. "I made that throw thousands of times. It sailed on me there, and nobody feels worse than me than putting the guy on second base there. I feel like it cost us the game tonight. "

Hunter Pence put runners on the corners with an infield single off Adam Ottavino (0-2), hitting a slow chopper that bounced over Ottavino to Descalso and just beating the throw.

Boone Logan came on and struck out Brandon Crawford. However, Kelby Tomlinson lined Logan's 0-2 fastball to left for single, scoring Posey.

"Just hoping to get a pitch that I could handle and get it in play there," Tomlinson said. "Even if I don't hit it well, hopefully my speed could beat it out or something -- trying to put the ball in play to get something going."

The win was just the Giants' second in the past six games and sixth in their past 16. San Francisco remains four games behind the Los Angeles Dodgers in the National League West and a half-game ahead of St. Louis and 1 1/2 games ahead of the New York Mets in the wild-card scramble.

After starter Jeff Samardzija gave up four hits and two runs in seven innings with a season-high-tying nine strikeouts and one walk, Giants manager Bruce Bochy used three pitchers for an out apiece in the eighth. The last was Javier Lopez (1-2).

Santiago Casilla worked the ninth. After a one-out walk, Parra grounded to second baseman Tomlinson, who started a double play that sealed Casilla's 31st save.

Casilla blew his seventh save of the season in the ninth Sunday at Chicago, leading to a Cubs win in 13 innings. The seven blown saves are tied for the second most in the majors.

"I know he's had some hiccups," Bochy said. "They all have. It's the nature of being in the bullpen, got to stay behind them. He's got great stuff. I just didn't feel like there's a need for a change right now. "

When Gorkys Hernandez led off the eighth with a single, it was a modest achievement for the Giants -- their fifth hit of the night. They had been held to four or fewer hits in five consecutive games, tying a major league record in the modern era (since 1900).

Trevor Brown followed with a single. Rockies third baseman Nolan Arenado made a dive to his left to snare Brown's hard smash, but Arenado, throwing from his knees, pulled second baseman DJ LeMahieu off the base.

After pinch hitter Ehire Adrianza sacrificed the runners, Colorado starter Tyler Anderson gave way to Jordan Lyles. Nunez brought Hernandez home, tying the game at 2, with a grounder off Lyles to shortstop before Angel Pagan grounded to first. Rockies manager Walt Weiss did not consider drawing his infield in with Nunez batting.

"I can't right there," Weiss said. "That's suicide. You got two guys in scoring position. You're at home; you'll play for the tie there. We'll give up the run and extend the game if we have to. On the road, that probably becomes a tougher decision."

Anderson pitched a career-high 7 1/3 innings, giving up two runs on six hits and two walks. He had a season-low-tying two strikeouts and recorded 10 outs on ground balls.

"Changeup wasn't as good today as it has been in the past," Anderson said, "so we had to make due with cutters and fastballs mostly. And when you do that, obviously guys are swinging because they all look like fastballs. So I was able to get them to put the ball in play a lot."

Samardzija continued to thrive in Denver. In six career games at Coors Field, including three starts, two this season, he is 2-0 with a 2.15 ERA.

"I think I've had success here because I haven't walked guys when I'm here," Samardzija said. "But that applies to any park, but it's magnified here, just because of outfielders playing deep and the ball flying when it's up."

NOTES: Rockies 2B DJ LeMahieu extended his career-high on-base streak to 23 games. ... Colorado RHP Eddie Butler, RHP German Marquez and C Dustin Garneau were recalled from Triple-A Albuquerque. ... Rockies INF Pat Valaika and 1B/OF Jordan Patterson had their contracts selected from Albuquerque. To make room for them on the 40-man roster, 1B Ben Paulsen and INF Rafael Ynoa were designated for assignment. ... Rockies CF Charlie Blackmon did not play for the fourth straight day due to lower back tightness. ... Giants RHP Jake Peavy (lower back strain) will be activated Wednesday. ... San Francisco 1B Brandon Belt, hitless in his past 18 at-bats, and CF Denard Span, hitless in his past 20 at-bats, were not in the starting lineup. Belt entered the game on defense in the ninth.