(Sports Network) - The Los Angeles Dodgers are starting to pull away in the National League West standings and will wrap up a three-game series against the Colorado Rockies today at Coors Field.

The Dodgers are 4 1/2 games ahead of Arizona in the NL West standings thanks to four straight wins and victories in 12 of their last 13 contests. They handed the Rockies a 5-1 setback on Saturday, as Russell Martin drove in a pair of runs to lead the offense. Angel Berroa drove in a run for Los Angeles. Starter Clayton Kershaw collected to the win, giving up just one run and four hits in six innings of work. Kershaw also struck out seven batters and issued two walks.

Greg Maddux will make his fifth start for the Dodgers on Sunday and he is 1-3 with a 5.96 ERA so far with his new club. Maddux, who is 7-12 with both San Diego and Los Angeles this season, has lost four of his last five trips to the mound.

Maddux was beaten by the Padres the last time out on September 8 in a 4-0 loss, yielding four runs and seven hits in six innings. The right-hander has given up two runs or more in each of his last four starts. In 30 career starts against the Rockies, Maddux is 16-8 with a 4.25 ERA through 192 2/3 innings.

Colorado has dropped seven in a row to throw a wrench in its playoff hopes. The defending NL champions are 10 1/2 games behind the Dodgers in the NL West. In Saturdays loss, Clint Barmes had two hits and the only RBI for Colorado, which got a lousy performance from starter Jorge De La Rosa. He was saddled with the loss after he gave up four runs on seven hits in five innings.

Aaron Cook will try to fare better when he gets the nod for the Rox on Sunday. Cook is 16-9 with a 4.16 earned run average, but is only 2-3 in the past five decisions. He did record a decision in a 5-4 loss at Atlanta the last time out on September 9, as he was reached for four runs and six hits in six innings of work.

Cook, a right-hander, beat LA with eight innings of one-run ball on June 4 and is 5-5 with a 4.18 ERA in 17 career games, 12 of which have been starts, in this series.

The Dodgers are 10-7 against the Rockies this season and ended a four-game slide in the series with a 3-1 victory on August 21 at Chavez Ravine.