Cook gave up a run in each of the first two innings but no more until center fielder Willy Taveras misjudged Tony Clark's deep fly ball to allow a seventh-inning run that gave the D-backs a 3-2 lead.
In all, Cook gave up three runs, two earned, and five hits in 6 1/3 innings, with three walks and four strikeouts. It was the fourth time Cook couldn't achieve win No. 17 to tie club record-holders Kevin Ritz (1996), Pedro Astacio (1999) and Jeff Francis (2007). But couple this with his last start, when he went six scoreless, and Cook is finishing his first All-Star season the way he wants.
After the All-Star Game, when he threw three scoreless but high-pressure innings for the National League on short rest, Cook struggled and eventually had to have a start backed up because of back stiffness. His numbers have dipped -- 11-6, 3.57 ERA before the break, 5-3, 4.75 after.
"It's definitely nicer when you're pitching well," Cook said. "Now I can get on a better page, feel better about my mechanics, the way the ball's coming out of my hand."
Also, if Cook has a say, and he expects to, he'll have one more chance at No. 17. Manager Clint Hurdle said the club is monitoring Cook's workload and is going day by day in its decision whether to give him one more start. His 211 1/3 innings are just 1 1/3 innings below the career high he achieved in 2006.
But Cook said he will campaign for one more chance.
The Rockies won Friday's first game of the series and had their chances Saturday, but ultimately fell to 3-11 against the D-backs this season. Cook wants to pitch at Chase Field during the Rockies' season-ending series with the D-backs next weekend.
"I don't think there will be too much question about that right now," Cook said. "It's not as much the 17th win as [the D-backs] are in a pennant race with the Dodgers, and I feel like I have to go out there and give it my best shot. I think I owe it to both teams.
"Unless the Dodgers call over and say they want somebody else to start, I'm going to go out there and try to take it."
Hurdle liked the way Cook found his rhythm.
"He threw everything he had at them," Hurdle said. "You want your guys to leave it on the field. He left it on the field tonight."
Ultimately, mistakes by the Rockies took Saturday's game away from Cook.
The D-backs' Chad Tracy knocked an RBI double in the first, and a run scored on a double-play grounder after Cook had given up two hits and a walk to open the second. But Cook bordered on dominant from there, holding the D-backs to one hit before leaving.
Jeff Baker, who singled in the Rockies' first run in the fourth (before Clint Barmes lined out and Ian Stewart struck out to end the threat) tied the game with a solo shot in the sixth off Doug Davis.
But with two on via Cook walks and one out in the Arizona seventh, Taveras made a long run from shallow center field for Clark's deep fly. However, the ball landed beside him and the go-ahead run scored.
"I think the wind got it," Taveras said. "It's tough, especially when you have 'Cookie' on the mound pitching so well. You should come up with that play."
The Rockies' Garrett Atkins tied it in the eighth with a sacrifice fly against Tony Pena (3-2).
Fuentes had a 0.94 ERA over his previous 29 games. Chris Young drew a leadoff walk and was at second when Drew went deep to right with the count full for his 19th homer of the season. A pitch before the homer, Drew lost track of the count and ran to first on ball three.
"He is human," Hurdle said of Fuentes. "He's been on a tremendous roll. He wobbled a little last night [in the ninth inning of a 3-2 Rockies victory] but got big outs, big strikeouts. Tonight, it just didn't happen."