DENVER -- Six starts into his Major League career, Chad Bettis is still learning how the slightest mistake can turn into serious trouble.
So when Hunter Pence crushed an inside 1-1 fastball, one that probably sailed a bit too high, over the left-field bleachers, Bettis (0-3) became a firsthand observer of just how costly such an error can be. ESPN estimated the ball traveled 476 feet, which would be the longest homer in the Majors this year.
He gave up another home run to Pablo Sandoval three pitches later, the first inning putting the Rockies in a hole they couldn't escape in a 5-3 loss to the Giants at Coors Field on Tuesday night.
"That ball was on the chalk inside, so he knew it was coming in and he cheated to it and you got to tip your hat," Bettis said. "Probably should've thrown a different pitch there, but you can go back now and always say that. It's incredible that he got to it still, but he did."
It was Colorado's second loss in five games, pushing it 10 games under .500 as the Dodgers lay siege to the rest of the National League West. Jhoulys Chacin will take the mound for Wednesday's series finale as the Rockies try to pick up their second consecutive series victory.
Bettis quickly settled down, lasting through the sixth inning, and allowed just one additional run over the next five innings. He departed after allowing four runs, striking out two and escaping a handful of dangerous situations.
"His makeup's pretty good," Rockies manager Walt Weiss said.
It was Pence's only hit of the night, but that bomb was enough to push San Fancisco past a scuffling Colorado offense.
"All my hits combined probably weren't hit as hard as his," said first baseman Brandon Belt, who went 4-for-5 with four singles.
While there was something positive to glean from Bettis' start, the Rockies offense had much less to cheer about, finishing 1-for-10 with runners in scoring position.
Colorado's best chance to rally came in the seventh when Corey Dickerson snuck a ball inside the third-base line to position runners at second and third. Jordan Pacheco scored on DJ LeMahieu's groundout, but the heart of the order -- Tory Tulowitzki and Michael Cuddyer -- couldn't add to the damage and stranded Dickerson at third.
Cuddyer finished 0-for-4, ending his 10-game hitting streak.
The Rockies got on the board in the third when Charlie Blackmon floated a ball deep into center, over Gregor Blanco's head, for a double to score Nolan Arenado from first.
Catcher Wilin Rosario cut the Giants' lead to one in the fourth when he slipped an RBI single through an infield gap to score Tulowitzki. That was the closest the home club came to mounting a comeback as no Rockies player other than Rosario had multiple hits.
Rosario was the club's lone offensive highlight Tuesday night, finishing 3-for-4 to improve to .429 with three doubles, two homers and 13 RBIs in his last eight games at Coors Field.
"I think he's made some adjustments to the way they pitched him, particularly in the first half [of the season]," Weiss said. "There's times where he's gone up there in the last three weeks or so and he's sitting on offspeed stuff, sitting on breaking balls and getting in tune to how they're trying to get him out and shooting some balls to the big part of the field."
In his second big league start in four seasons, Yusmeiro Petit (1-0) allowed just six hits and two runs over six innings, striking out six and walking three. That proved enough for his first Major League win in four years.
"He just threw strikes -- strike one and worked from there," Giants manager Bruce Bochy said. "Kept his poise out there. He pounded the strike zone with all of his pitches and threw quality strikes. He's been around, knows what he's doing out there. He showed it tonight."
As the Rockies offense slowed, San Francisco kept tacking on runs. Hector Sanchez singled to right to drive home Belt in the sixth, and Blanco moved to third after his leadoff double off reliever Adam Ottavino on an error by center fielder Blackmon in the seventh. Blanco crossed home on a Marco Scutaro sacrifice fly for the Giants' fifth and final run.
Colorado never produced more than one run in an inning, the Giants' early tear enough for a road victory. In the eyes of Rosario, who agreed that Pence unloaded on a decent pitch, the Rockies were just a strike away from averting trouble.
"I think [Bettis] missed a couple pitches in the zone and we can't execute the last pitch," Rosario said. "Every hitter we got two strikes, and we couldn't execute the one pitch to make an out. I think that's why he got a little bit out of control and we gave up three runs."
Ian McCue is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.