In Japan, where teams always have one day off a week, teams carry six-man rotations and each guy pitches once every seven days. Over here, where days off come every other week, guys mostly pitch every five days... until some of them inevitably get hurt and reinforcements are called in from the bullpen, the minors, or the waiver wire.
The Rockies have had worse-than-average luck when it comes to needing to replace starters in the last three seasons, but at the very least they seem to have a general manager who understands that five starting pitchers isn't even close to being enough. Last season was an extreme example, as 60% of the Rockies' working rotation washed out (all within a few weeks of each other) and the team, as you may remember, got better, thanks to rookies Ubaldo Jimenez and Franklin Morales and the amazing, ongoing job of jury-rigging Clint Hurdle managed to pull off in the fifth starter's spot. In case you managed to overlook it: On August 12th, 2007, Tim Harikkala started a game for the Rockies. And they won it.
So if Colorado manages to get through the entire 2008 without any repeat Harikkala performances, you'd have to say they'd solidified the rotation. Mark Redman, who's almost certainly better than Tim Harikkala, played a bit part on last year's team and is competing to play a larger role this season. Kip Wells, who also has a name you might remember, doesn't have a guaranteed contract like Redman, but if he dazzles them down in Tucson, he could be in the April rotation. With the exception of Josh Fogg, with whom the Rockies reasonably could not have expected to catch lightning in a bottle for three seasons running, all of the starters who finished last year are still under contract -- Morales, Jimenez, Aaron Cook, and Jeff Francis. Also returning is Jason Hirsh, who missed the second half with a non-pitching injury. Hirsh had his leg broken by a J.J. Hardy comebacker in August during a game I attended. The story at the time was how Hirsh stayed in after the incident -- Hardy was the second batter of the game -- and pitched six scoreless innings. That was both the highlight and the lowlight of Jason's season, since I don't recall him ever pitching nearly as well on two non-broken legs.
(It is funny to read what I wrote about the injury on August 8th, 2007: "Who's to say the Rockies can't weather the loss of two of their first-choice starters? Ubaldo Jimenez is already better than Hirsh and maybe Franklin Morales will replicate Lopez's surprising early-season performance." Wow, just you wait, past me! Jimenez was indeed much, much better than Hirsh, and while Morales was erratic it was the bullpen that did a heroic job making up for the loss of the innings-munching Lopez.)
So, as for this year, you have Francis, Cook, and Jimenez. No questions there. I imagine that everyone involved with the Rockies would greatly prefer that Morales throws well enough in the spring to keep his spot in the rotation; his major-league service clock has already begun ticking and besides, he's left-handed. Hirsh is a bit of a question mark. He's a flyball pitcher and a fastball-curve guy to boot; at Coors Field, that skill combination usually leads to guys getting dragged from the mound in a straitjacket. What's more he has not only Wells and Redman but also now Josh Towers, a vaguely interesting name, with whom to compete. Towers had a lot of hits drop in against him last year but his peripherals look OK... he had a higher strikeout rate and lower walk rate than both Hirsh and Morales last year. I'm a little surprised he couldn't find a team willing to give him a firmer promise of a starting role, to tell you the truth, but maybe Towers is self-aware enough to know his future is as a super swingman. Dan O'Dowd certainly envisions him as both starting and relieving. I hope that the Towers acquisition doesn't cause Taylor Buchholz to get lost in the shuffle; the forgotten third man from the Willy Taveras-and-Jason Hirsh-for-Jason Jennings trade put in some excellent long relief work down the stretch last year (inspiring a few of us Rockies fans to ask why Buchholz wasn't getting even a sniff at a start... dude, one more time, Tim Harikkala).
So your starting depth chart looks like this:
(Very tentatively) Jason Hirsh
And that's not so bad. Scratch one or even two of those names from the top five (save the Channel, whom I suspect few Colorado fans even realize the full value of last year) and you're still right there with the other teams in the division besides San Diego, if a little less top-heavy and bottom-slack. And on the off-chance that the Rockies aren't deluged with pitching injuries (which would be a first at least since I've been living in Colorado), they could be really good.