SAN FRANCISCO -AP- Tyler Chatwood's extra work on offspeed pitches during spring training made a huge difference Saturday.Chatwood pitched 5 2/3 perfect innings before Chris Marrero's single and finished with a two-hitter for the Colorado Rockies in his first big league shutout, a 5-0 win over the San Francisco Giants.Chatwood (1-2) struck out four and walked one, lowering his ERA from 6.35 to 3.54. He threw 67 of 105 pitches for strikes in his second complete game in 91 major league starts. "The first two outings I didn't feel like I threw the ball bad, but I gave up homers that killed me," Chatwood said. "Today my curveball was there, and I think that was a difference-maker. That separation in velocity was big for me today."He retired 17 consecutive batters before Marrero lined a single into right field. Joe Panik singled leading off the seventh."The curve, change cutter and slider all came into play today," Rockies manager Bud Black said. "The mix of pitches was something we've talked about, and he put that into play today. It was an outstanding effort and one of the best games I've seen in a while just from a pure pitching standpoint."Chatwood's teammates didn't let on that he was flirting with perfection. A sellout crowd ATT Park did."I realized it because every time I was on deck or if I stepped out of the dugout all the fans were saying. `I hope you blow it," Chatwood recalled.Nolan Arenado had three hits, including a home run off Matt Moore (1-2), who allowed five runs, 10 hits and three walks in 5 2/3 innings.Arenado's fourth home run this season put the Rockies ahead 1-0 in the third, and Charlie Blackmon hit a two-run single in a three-run fourth that included Dustin Garneau's RBI double.Stephen Cardullo added a run-scoring single in the fifth.Giants left fielder Jarrett Parker broke his right collarbone crashing into the wall on a running catch, robbing D.J. LaMahieu of an extra-base hit with two outs in the fourth inning. After the collision, Parker sprinted toward the infield, stopped and dropped to his knees on the outfield grass. He grimaced, was examined by trainers and was replaced by Aaron Hill."You know you are all in when you make a play like that," Giants manager Bruce Bochy said. "You're focused. I had no idea he was going to catch that ball. To see him stay locked in was a hats-off moment to him and a huge play, it kept us in the game."