The Marlins, with three runs already in the third inning, had two on, one out and cleanup hitter Mike Jacobs batting. But, unworried and unhurried, Cook needed just two pitches to force a double-play grounder and put the Rockies on a smooth path to a 6-3 victory in front of 11,534 at Dolphin Stadium.
The sequence illustrated the difference in Cook (8-6) during his current run -- he is 4-1 with a 2.66 ERA in his last five starts -- and his struggles at the beginning of the year.
It's the type of pitching that can make all the difference for the Rockies, who entered the night three games off the lead in the National League West.
Considering that they didn't make a trade at Tuesday afternoon's non-waiver deadline, they believe that the difference-makers may already be wearing purple pinstripes. They certainly felt that way about Cook back on Opening Day, when they named him the starter.
Cook, however, is beyond trying to do things in a big way. Having seen a five-run lead reduced to two, Cook was facing a situation that escaped him earlier in the year. He had a good plan, which was confirmed by a visit from rookie catcher Chris Iannetta, who worked his last five starts.
"There's definitely a difference in the thought process," said Cook, who gave up three runs, two earned, in 7 2/3 innings. "Instead of trying to throw my hardest sinker right there, I'm just trying to throw my heaviest. Iannetta came out and said, 'I just want your good sinker right here, nothing too hard. Let him hit it on the ground.' "
It was not quite as dominating a performance as Cook's last start, when he needed just 74 pitches for a complete-game victory over the Padres at Coors Field. But he was effective in throwing his 106 pitches.
After besting Jacobs, Cook -- who struck out five and walked two -- didn't yield another hit until Alfredo Amezaga's single to open the eighth. Cook followed the single by forcing pinch-hitter Joe Borchard into a double play.
Ex-Marlin Jorge Julio replaced Cook after Hanley Ramirez's two-out double and struck out Dan Uggla. Rookie Manny Corpas pitched a perfect ninth with one strikeout for his seventh save in as many chances.
"Aaron was very good again tonight," manager Clint Hurdle said. "He's on a roll. He's just in a good zone -- less effort, more power, more sink, more crispness to his slider."
The Rockies' all-right-handed-hitting lineup -- Jamey Carroll, Ryan Spilborghs and Jeff Baker started in place of, respectively, Kazuo Matsui, Brad Hawpe and Todd Helton -- chased Marlins starter Scott Olsen (8-9) with seven runs and six hits in five innings.
"It's always good whenever you can get runs on the board early. It's a chance to let your starter settle in," said Garrett Atkins, who had the biggest hit, a three-run double during the Rockies' four-run third at the end of an eight-pitch at-bat.
Matt Holliday added three hits, including two doubles.
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.