PHOENIX — For the fourth straight season, Brandon Webb will be the opening day starter for the Arizona Diamondbacks. For once, though, he’ll be at home.

The Arizona ace takes the mound against Colorado’s Aaron Cook on Monday when the Diamondbacks open their season at home for the first time since 2005.

Cook’s the unquestioned leader of the Colorado staff with Jeff Francis out because of season-ending shoulder surgery.

It will be the second opening day start for Cook (16-9, 3.96 ERA), who had a career-high in wins last year. His first opening day start was two seasons ago.

“It’s part of the maturing process,” Cook said before the Rockies worked out at Chase Field on Sunday. “Last year I was able to pitch well enough that Clint (Hurdle) decided to give me opening day. But I’ve got to go out there and treat it like every other start. Hopefully I’ll get 34, 35 of them this year and there’s not one that’s going to mean more than the other. I’ve got to go out there with that sort of attitude.”

Cook won’t get wrapped up with who’s on the mound for the other team.

“Me and Webb have faced each other probably about seven or eight times in our careers,” he said, “He’s an ace pitcher, Cy Young, last year he pitched great. You’ve got to go out not worrying about who’s on the mound for the other team. I’ve got to worry about keeping our team in the game.”

Webb (22-7, 3.30 ERA) led the NL in victories last year and was runner-up for the Cy Young Award for the second season in a row. He won it in 2006.

The Rockies bolstered their bullpen on Sunday by acquiring right-hander Jason Hammel from Tampa Bay for minor league pitcher Aneury Rodriguez.

Colorado will have a pair of new everyday starters in center fielder Ryan Spilborghs and left fielder Seth Smith. Smith replaces big-hitting All-Star Matt Holliday, traded to Oakland in the offseason.