Los Angeles Dodgers manager Don Mattingly said Clayton Kershaw has nothing to prove the way he’s been pitching. The young left-hander, though, might need to prove to himself he can beat the Colorado Rockies.Kershaw tries to win a career-best fourth consecutive start Tuesday night when the host Dodgers look to post their fourth straight victory and snap a 15-inning scoreless streak against Rockies right-hander Jhoulys Chacin.With a season-high 12 strikeouts and only one walk, Kershaw (11-4, 2.72 ERA) was removed from Wednesday’s 1-0 win at San Francisco after tossing eight innings of three-hit ball.Mattingly admitted that he thought twice about letting the young Texan try to notch his fourth complete game of the season, but he ultimately replaced the young left-hander after his 112-pitch outing ran his scoreless streak to 23 innings.”(Kershaw) doesn’t need to take any more steps — he’s pretty much on top and just has to stay there,” Mattingly told the Dodgers’ official website.Kershaw has a major league-leading 167 strikeouts and 10.32 strikeouts per nine innings, but he is 0-1 with a 6.75 ERA in two starts versus Colorado — both in Denver — in 2011. After surrendering three runs in a 3-0 loss April 5, Kershaw gave up six runs and seven hits in six innings in a 9-7 defeat June 9.The left-hander, though, will face a Rockies team that has batted .185 and totaled eight runs while losing three straight. Colorado (48-55) struck out 10 times and had just five singles in Monday’s 8-5 series-opening loss, but it scored four times in the ninth and had the go-ahead run at the plate.”That inning obviously didn’t work out very well for us, but we didn’t go down easily,” said manager Jim Tracy, whose team has dropped 11 of 14 on the road and is seven games below .500 for the first time since June 8, 2009.The Dodgers (46-56), meanwhile, are working their way up the West standings with four wins in five games and a 7-1 mark at Chavez Ravine after dropping six of seven there.Colorado’s starters have a combined 6.67 ERA during the team’s 3-7 slump, but the club is hoping Chacin (8-7, 3.60) can get it back on track with another strong outing in this matchup.Chacin is 2-0 with a 0.00 ERA in two starts versus Los Angeles in 2011. After going seven innings in the April 5 victory, he fanned nine in eight shutout innings of a 6-5 win June 10.However, the right-hander is 0-3 with a 6.75 ERA in his last five outings after walking a career-high seven and giving up five runs in Thursday’s 9-6 loss to Atlanta.”I think that was the worst start I’ve had in my career,” he said.Chacin, 0-3 with a 5.82 ERA in his last three road starts, went eight shutout innings in a 12-2 win Sept. 18 in his last start at Dodger Stadium.Andre Ethier, who had a two-run homer and three RBIs on Monday, is 5 for 13 with six RBIs in four home games against Colorado this season. He is 6 for 13 with two doubles off Chacin.Matt Kemp, though, has just three hits in 20 at-bats against the right-hander.Troy Tulowitzki (32 at-bats) and Todd Helton (26) each have seven hits — including a homer — versus Kershaw. They also have combined to strike out 17 times against the left-hander.