Carlos Gonzalez's three-run triple and Ian Stewart's two-run shot in the first gave Chacin (2-0) the advantage, but not a false sense of security.
"Don't change my plan -- just throw a strike," Chacin said. "That's the key for me."
With a fastball capable of 94 mph and a curve, slider and changeup even pitchers with far greater experience would envy, Chacin, 22, has plenty of ways to throw strikes and baffle batters. He used them all, but properly.
"One of the things you concern yourself with, with a young kid, is when you stake him to a lead like we did with six in the first inning, how is he going to handle that?" Rockies manager Jim Tracy said. "Is he going to get a little too excited and want to hurry his way through this thing?
"But he kept himself completely under control."
The Rockies are 4-4 on a key early-season National League West road trip and have a chance end it on the plus side -- with ace Ubaldo Jimenez starting on Sunday afternoon. Chacin (2-0) is a big reason for the success and could be pitching himself into a key role for the rest of the year.
Injuries to Jeff Francis (left shoulder tightness), Jorge De La Rosa (torn ligament band in his left middle finger) and Jason Hammel (strained right groin) opened spots for Chacin and Esmil Rogers (0-1, 6.39 ERA). While Rogers could be the odd man out if Hammel is activated this week, Chacin has pitched himself into position to stay no matter who else becomes healthy when.
"I don't know; I can just control how I pitch and help the team win," he said.
Chacin threw an inning of scoreless relief after being called up from Colorado Springs and held the Giants to one hit with nine strikeouts in winning his first start last Sunday. Chacin was just as daunting for Dodgers hitters Saturday. Just three times did the Dodgers have more than one baserunner.
Chacin was most unflappable after yielding Andre Ethier's leadoff double in the sixth. Chacin extracted a fly ball from Manny Ramirez, a harmless liner from James Loney, hit Casey Blake and forced Blake DeWitt into another fly.
"When he's able to pitch ahead like that, throw strikes, it's tough," DeWitt said.
Chacin left with runners at the corners and one out in the eighth. But Randy Flores forced Loney into a double-play grounder. Joe Beimel threw a one-hit ninth to complete the Rockies' fourth shutout of the season.
Before the promotion, Chacin was 3-0 with a 1.69 ERA in four starts for Colorado Springs. Veteran catcher Paul Phillips, who was with Chacin in Colorado Springs and has caught both Major League starts, said Chacin is even better now.
"I'm seeing way more control," Phillips said. "His demeanor is awesome. He's throwing the ball with confidence. It's a lot of fun to catch him."
The Rockies' first four plate appearances against Dodgers knuckleballer Charlie Haeger (0-4) produced a Seth Smith single, three walks, a 1-0 lead -- and loaded bases. Then Gonzalez launched his triple to raise his RBI total to 18 in the past 11 games and chase Haeger after 22 pitches with no outs.
Stewart greeted reliever Ramon Ortiz with a two-run homer to dead center. Stewart, who added an RBI single in the second, has six homers this season, and the Rockies' only two long balls of the road trip.