Lincecum will try to become the first Giants pitcher in 15 years to go 5-0 in March and April on Tuesday when they continue their three-game series against the Colorado Rockies.San Francisco (12-15) has had its share of problems with its rotation through the first month of the season, highlighted by Monday's demotion of winless Barry Zito to the bullpen.Lincecum (4-0, 1.23 ERA) has emerged as the Giants' unquestioned ace, going 3-0 with a 1.07 ERA in four starts, and also winning in relief in his season debut on April 2 against the Los Angeles Dodgers.He is riding a scoreless innings streak of 16 1-3 after he lasted 6 1-3 innings in a 1-0 win at San Diego on Thursday. He allowed four hits, struck out nine and overcame a season-high five walks to outduel the Padres' Chris Young."I struggled a little bit with my control," Lincecum said. "It's still nice to pull out a win when you're off."Lincecum is trying to become the first Giant to open 5-0 in March and April since John Burkett in 1993.The right-hander went 1-0 with a 4.50 ERA in two starts against the Rockies last season as a rookie. Colorado shortstop Troy Tulowitzki was 0-for-6 with four strikeouts against him in those games.San Francisco handed Colorado (10-16) its fourth straight loss, 4-0 on Monday. Starter Matt Cain and three relievers combined to scatter eight hits by the Rockies, who have also dropped eight of nine.Ray Durham had two of the Giants' four steals. They have 30 stolen bases in the opening month for the most in San Francisco history, topping the 1999 team's 28 through the end of April.Despite Monday's loss, Rockies third baseman Garrett Atkins went 2-for-4 to extend his hitting streak to 13 games -- the longest current run in the majors. First baseman Todd Helton, however, had his 10-game hitting streak snapped after going 0-for-4 and striking out with two runners on base to end the game.Colorado's Aaron Cook (3-1, 2.91) looks to win his fourth straight start. He has posted a 2.57 ERA in winning his last three outings, including a 4-2 win over the Chicago Cubs last Thursday in which he gave up two runs over eight innings."We needed a shot in the arm from a starter. He gave it to us," Rockies manager Clint Hurdle said.The right-handed sinkerballer, who is limiting opponents to a .200 batting average, went 2-0 with a 2.40 ERA in two starts against San Francisco last season. The Rockies had lost his previous seven starts to the Giants, with Cook going 0-4 and compiling a 4.33 ERA in that span.San Francisco's Randy Winn (2-for-17) and Rich Aurilia (3-for-18) have both fared poorly against Cook in their careers.