The right-hander looks to move into a tie for the major league lead in wins as he takes the mound in the opener of a four-game set against the last-place Washington Nationals on Monday night
Cook (14-6, 3.53 ERA) is tied with Cleveland's Cliff Lee, the New York Yankees' Mike Mussina and Joe Saunders of the Los Angeles Angels for second in the majors in victories, one behind Arizona's Brandon Webb.
Of the four chasing Webb, though, Cook could be one of the bigger surprises after he went 8-7 with a 4.12 ERA last season. The seven-year veteran appeared in his first All-Star game last month, and has won all three of his starts while posting a 3.27 ERA since the break.
But Cook had his worst outing over that stretch on Wednesday, allowing four runs and nine hits with three walks over seven innings in a 7-4 win at Pittsburgh.
"The term is effectively ugly," said Cook, who is 1-0 with a 2.63 ERA in six games -- three starts -- against the Nationals franchise. "The team gave me some runs early, and that made things easier."
Despite Cook's outstanding season, Colorado's rotation has a 5.11 ERA to rank better than only Cincinnati (5.14) and Pittsburgh (5.83) in the NL.
Colorado (51-62) closed out a 6-4 road trip with a 3-2 win at Florida on Sunday as Seth Smith drove in the go-ahead run with a pinch-hit single in the ninth inning.
Now, the Rockies look to carry some of that momentum into the opener of a 10-game homestand. They went 11-2 at Coors Field last month, hitting .340 with 24 homers and 106 runs.
Colorado also has won seven straight at home from the Nationals, outscoring them 64-38.
Matt Holliday, Colorado's other All-Star and among baseball's leaders with a .347 batting average, was terrific at home in July, batting .440 (22-for-50) with six homers and 19 RBIs. He's hit safely in nine straight home games against the Nationals, batting .514 (18-for-35) with five homers and 16 RBIs.
Holliday hit .375 (15-for-40) with four homers and six RBIs on the road trip.
The Nationals (41-70) are a major league-worst 18-37 on the road this year, but also will be trying to match their season-high four-game winning streak set from April 27-May 1. After dropping nine in a row, Washington completed a three-game sweep of Cincinnati with a 4-2 win on Sunday.
"Psychologically, it has to be very good because we just got swept three series," Nationals manager Manny Acta said. "If we had just won this series it would have been great, but getting the sweep is a lot better because it puts some space between the days that you had that losing streak."
To keep the run going, the Nationals will send Tim Redding (7-6, 4.34) to the mound. The right-hander leads the team in wins this season, but is 0-1 with a 3.00 ERA in four games -- three starts -- against Colorado.
Since last month's break, Redding is 0-3 with a 7.88 ERA. He was tagged for seven runs and 10 hits in four innings of an 8-5 loss to Philadelphia on Wednesday.