The D-backs' huge turnaround last season was spurred by an improved pitching staff, and the starting rotation set the tone for that.
While ERA has its limitations as a stat, it does provide a peek into just how much better Arizona's starting staff was in 2017.
After finishing with a 5.19 ERA in 2016, which was 29th in the Majors, the D-backs' starters compiled a 3.61 mark in 2017, third best in all of baseball.
The D-backs' success in 2017 began with its starters, and if the team is to once again make a postseason run, the rotation will be expected to lead the way. MLB.com is taking a look at the projected rotation of all 30 teams ahead of Spring Training. Here's how the D-backs might stack up:
ROTATION IF SEASON STARTED TODAY
RHP Zack Greinke
LHP Robbie Ray
RHP Taijuan Walker
LHP Patrick Corbin
RHP Zack Godley
STRENGTH
The D-backs head to Spring Training with their rotation already in place. Once of this group's strengths was its ability to pitch deep into games in 2017, something manager Torey Lovullo encouraged. The 2016 version ranked 20th in the Majors in innings pitched, but last year's group tossed a combined 941 1/3 innings, fourth most in MLB.

By compiling that many innings, the starters put less pressure on the bullpen, and as a result, the 'pen responded with a much better year as well.
In Greinke and Ray, the D-backs have a pair of aces at the top of the rotation. Walker took a step forward in 2017, while Corbin bounced back from a disappointing '16 and Godley came out of nowhere to fill in for the injured Shelby Miller, delivering quality start after quality start.
QUESTION MARK
The D-backs don't have a ton of starting-pitching depth after the first five, especially with Archie Bradley seemingly ticketed for the bullpen again.
Miller will not be back until midseason as he recovers from Tommy John surgery, so the team would need to rely on its farm system for any help until then.

Left-hander Anthony Banda and righty Braden Shipley both made starts for the team in 2017 and would seem to be the first backup options at this point. Matt Koch could also get a look. Another couple of names to keep an eye on are righties Jon Duplantier and Taylor Clarke, who are ranked as the team's No. 2 and 3 prospects, respectively, by MLB Pipeline, but will likely not be ready until later in the season, if not '19.
WHAT MIGHT CHANGE
There is still a chance the D-backs will deal one of their starters before camp opens, with the two names mentioned most this winter being Greinke and Corbin.
Dealing Greinke still seems unlikely given the four years and $126.5 million he has left on his contract. With the D-backs looking to contend in 2018, would they really feel comfortable dealing their ace?

Corbin, on the other hand, is set to make more than $8 million in his final year of arbitration, and if the team were to deal him it would free up some money to improve in other areas.
Before dealing a starter, though, D-backs general manager Mike Hazen made it clear during the Winter Meetings that the team needs to feel it could acquire a replacement.
"There would have to be some other path that you would feel comfortable you'd be able to replace that starting pitcher with," Hazen said. "Wherever that was, I would like to have a plan in place if we did that."