When Arizona has had success in the past, it has tended to be built on good starting pitching, whether the tandem of Johnson and Schilling in the early 00's, or Webb's Cy Young-worthy performance in 2007. The loss of Brandon proved disastrous for the team in 2009: while Haren stepped up, especially in the first-half of the year, our lack of rotational depth was certainly cruelly exposed. With the loss of Garland and Davis this winter, the front-office made a blockbuster trade which sent Scherzer and reliever Daniel Schlereth to Detroit, and brought in a pair of starters to fill out the middle of the Diamondbacks' rotation.

After the jump, we'll take a look back at what transpired in the year gone by, and see what we might expect in 2010, given that 60% of our rotation will have changed from Opening Day 2009.

2009 Performance
Dan Haren: 33 starts, 229.1 IP, 14-10, 3.14 ERA, 1.003 WHIP
Doug Davis: 34 starts, 203.1 IP, 9-14, 4.12 ERA, 1.505 WHIP
Max Scherzer: 30 starts, 170.1 IP, 9-11, 4.12 ERA., 1.344 WHIP
Jon Garland: 27 starts, 167.2 IP, 8-11, 4.29 ERA, 1.431 WHIP
Yusmeiro Petit: 17 starts, 89.2 IP, 3-10, 5.82 ERA, 1.517 WHIP
Billy Buckner: 10 starts, 77.1 IP, 4-6, 6.40 ERA, 1.591 WHIP

The list above is important as much for who isn't on it, as who is. Brandon Webb, who had pitched more innings in the National League than anyone else over the preceding five years, managed one start and four innings in 2009, before being shutdown - initially temporarily, then permanently, leading to surgery on his shoulder in August. His replacements did not fare well. Over a total of 37 starts, the Five-Headed Beast of Webb Replacement [Petit, Buckner, Bryan Augenstein, Daniel Cabrera and Kevin Mulvey] went 7-20 with a combined ERA of 6.11. However, Buckner fared significantly better at the end of the year, after adding a cut fastball to his repertoire.

Haren had a brilliant first three months of the season and was arguably unfairly overlooked to start the All-Star Game for the National League. However, his BABIP regressed strongly in the second-half, in part leading to an ERA of 4.62 after the break, compared to just 2.01 before it. Davis was... Well, Doug was Doug, allowing far too many base-runners, but somehow surviving. In the new millennium, three qualifyiing pitchers in the majors had a season WHIP of 1.5 or above and an ERA+ better than 110. Davis is two of them (2007 and 2009) - while, curiously, the third also played for us (Webb in 2004). Over three years here, Davis had a WHIP of 1.542 and an ERA+ of 110. No-one else, over this time with a 110 ERA+ and 300 IP, even had a WHIP at 1.4.

Scherzer certainly blossomed this year, becoming a full-time starter in the majors and striking out more than a batter per inning. He did continue to have an issue with pitch-count: his average of 4.14 per batter faced trailed only Clayton Kershaw (4.31) in the majors among qualifying starters. Finally, Jon Garland delivered a solid year, pretty much in line with what we expected from him, making 27 starts with an ERA+ of 107, before being traded to the Dodgers - in the middle of a game against them. All told, there weren't many teams in the majors who could boast four starters with 150 innings and an ERA+ of 100+ [the Cubs and Giants did too, while the Rockies had five]. However, a large part of that work was undone every fifth day, by our sub-replacement level Webb stand-ins.

2010 Depth-chart and Projections

1. Dan Haren: 34 starts, 3.04 ERA, 17-7
   
2. Brandon Webb: 26 starts, 3.50 ERA, 12-7
3. Edwin Jackson: 34 starts, 4.07 ERA, 13-10
4. Bryan Augenstein: 21 starts, 4.97 ERA, 6-8
5. Ian Kennedy: 16 starts, 5.00 ERA, 3-5
6. Rodrigo Lopez: 21 starts, 5.00 ERA, 6-9
7. Billy Buckner: 29 starts, 5.05 ERA, 9-13
   

[I used ZIPS for these, as I don't have access to the Hardball Times projections for all the above - which is why the starts add up to more than 162 games] I think it probably isn't too much an exaggeration to say the Diamondbacks 2010 season hinges more on the returning Brandon Webb than any other player on the roster. If he comes back to full form - and though it's early days, the signs are hopeful - then the team's rotation could be the equal of just about anyone else in the league. A 1-2 punch of Webb and Haren provides a foundation upon which any team would be happy to build. However, an ineffectual or injured Webb would mean Jackson moves up to become our #2...and  let's just say, things get decidedly murky after that. We'll be watching Opening Day on pins and needles.

With Haren, the question is going to be, whether he can sustain himself for the entire season. After 187 starts,  and more than 1,200 innings, the table below gives Dan's splits for each month as we go through the year. As you'll see, he's brilliant through June, but then regresses sharply to the mean. Is it stamina? Or just chance? The latter is suggested because Haren's BABIP is consistently well below .300 for the first three months (ranging from .238 to .273), but is then above it for the last three months (.307-.340). That's odd, given this is generally supposed to be something largely outside a pitcher's control.

Perhaps almost as key as Webb will be the two new arrivals, Jackson and Kennedy, who are likely to be the #3 and #4 starters. The former is perhaps more of a known quantity, with 110 major-league starts under his belt. He certainly seemed to put it together last year in Detroit, but isn't that far removed from a poor 2007, going 5-15 with a 5.72 ERA for Tampa. He did walking a lot less people now, however, and the move to the NL should also help, though the projection systems are distinctly unimpressed - CHONE and Marcel are in the 4.3 range, with Bill James all the way up at 4.75. We'll be hoping for better than that: and in particular, that he avoids the Harenesque fall in the second half of the year, which he showed in 2009 [ERA going from 2.52 to 5.07]

The wild-card is Kennedy, who has made only 12 major-league starts, and missed a lot of playing time last season with an aneurysm in his right armpit. That shouldn't trouble him going forward, but he remains unproven. The minor-league numbers are good - 2.14 ERA over 22 starts in Triple-A - but how will he play out against major-league hitters? The final spot in the rotation appears to be Billy Buckner's at this point, based on his good form after returning from the minors in September. However, Augenstein and Lopez are other candidates, and if the latter can live up to expectation (in the 4.7 to 5.0 ERA range), would not be a bad emergency option to have in Reno.

Overall, there is the potential for Arizona to have a starting rotation second to none in the league, though this would require a lot of pieces to fall into place: Webb to be healthy, Haren avoids the second-half slump, Jackson to reproduce the form of last season, Kennedy to show he can handle major-league pitching, Buckner's cut fastball is the weapon he needed in his locker, etc. On the other hand, there is also the potential for a complete meltdown, if things go the opposite way. The reality, as in most things, is likely somewhere in the middle, but it all seems to hinge on Webb's arm. Until April, that's going to remain a huge question-mark; however, when the seasons starts, we should fairly quickly get a feel for how much our hopes have a solid foundation.