Which NL West team has the best rotation?

After handing Zack Greinke an average of $34.3 million a year and trading an enormous amount of future value to acquire Shelby Miller, the Diamondbacks have made a run at possessing the best rotation in the division.

From a fan perspective, even if one does not agree with the details and future cost of the transactions, one must appreciate the willingness of the front office to go for it. The Diamondbacks are clearly looking to put their new uniforms on a winning team by prioritizing short-term improvements, so while the loss of Swanson may sting down the road, their aggressive transactions will allow their current starting five to compete with the best in their division.

MORE: Who's got the best bullpen in baseball? | The worst pitchers of the 21st century

While the Diamondbacks have garnered most of the headlines, their division rivals have not simply stood still. The Giants have spent more than $200 million on two pitchers with top of the rotation potential and the Dodgers, after missing out on Greinke and Hisashi Iwakuma, signed Scott Kazmir and stand to gain with the imminent return of Hyun-jin Ryu and the eventual return of Brandon McCarthy. The Padres, in spite of rampant trade speculation, continue to hold their trio of high-quality arms.

This is a fascinating but wildly expensive arms race, as NL West teams have dished out close to half of a billion dollars on starting pitching this offseason. As things slow down around the holidays, let's take a step back and find out which team currently possesses the best rotation in the division. Did the Diamondbacks' shiny new acquisitions do enough? Did the Giants' two signings push them over the edge? Do the dark horse Padres have a trio that quietly pushes them to the top? Does the best pitcher in the league also front the best rotation in the division? Starting with the Diamondbacks, here are the 2016 NL West rotations and statistical projections.

Arizona Diamondbacks

Projected Rotation: Zack Greinke, Shelby Miller, Patrick Corbin, Robbie Ray, Rubby De La Rosa.

The acquisitions of Greinke and Miller have rebuilt a previously poor rotation from the top down. Greinke gives them a legitimate ace who can compete with the other aces in the division, while Miller, along with top holdover Patrick Corbin, slot in nicely behind him to give the Snakes a strong top three.

Miller has posted sub-4.00 ERAs in all three of his full seasons in the league but some projection systems see his performance as unsustainable. No, we are not concerned with his 17 losses largely due to a lack of run support, but we are concerned with his pedestrian 4.08 career xFIP, below average 9.2 percent swinging strike rate, and for a pitcher with just over a 20 percent career strikeout rate, an uncomfortably high 1.24 career WHIP. Perhaps the continued development of Miller’s cutter can prevent the forecasted regression, but there is a reasonable chance that his debut in the desert does not come close to justifying the enormous price paid for his services.

Of the three incumbents, Patrick Corbin is the most established and projects as a solid number 2/3 starter. Questions about his durability will arise as he looks to pitch a full season despite missing all of 2014 and half of 2015 with injuries. Robbie Ray, a 24-year-old pitching prospect in his third organization, posted 2.1 fWAR in his first extended opportunity in the league. It is unlikely that he will improve on his 3.52 ERA last season, but even with the projected 3.92 mark, Ray is a quality option in the back of the rotation. Rubby de la Rosa’s stuff remains ahead of his outlook, but he retains some upside and has a chance to provide value in the five slot. In the event that he does not, former top pick Archie Bradley could step in and get an long look.

2016 Steamer projections for the Diamondbacks' rotation are shown in the table below.

All Steamer projections courtesy of FanGraphs.

This is a balanced group with a legitimate ace in Greinke, a solid pair behind him in Corbin and Miller, a stable number four starter and two potential number five starters with upside. As a whole the Diamondbacks are solid, but there are many other quality arms in the division.

Colorado Rockies

Projected Rotation: Jorge de la Rosa, Chad Bettis, Jordan Lyles, Jon Gray, Tyler Chatwood

Jorge de la Rosa has no business fronting a rotation, but he has been a steady pitcher for the Rockies. Former top pick Jon Gray posted far better peripheral statistics than traditional statistics last season and is a strong bet to enjoy a breakout season in his first full campaign in the majors. Chad Bettis emerged to post 1.8 WAR last season, and the former second round pick is projected to post a similar total this year.

Rounding out the rotation are Tyler Chatwood and Jordan Lyles. Chatwood, acquired from the Angels, did not pitch at all for the Rockies in 2015 as he recovered from a second Tommy John surgery. Colorado will be hoping he can regain his 2013 form, when the righty posted a 3.15 ERA in 111.1 innings. Lyles, who joined the Rockies in the trade that sent Dexter Fowler to Houston, has been steady but unspectacular in his first two seasons with the club. The righty suffered a 5.14 ERA last season, but his 3.79 FIP suggests that he deserved much better. Former top prospect Eddie Butler got a taste of the show in each of the past two seasons but has failed to establish himself with the parent club. He has good stuff but a career 4.63 walk rate in the majors has significantly hindered his role.

2016 Steamer projections for the Rockies' rotation are shown in the table below.

The Rockies have five pitchers projected to post at least 1.0 fWAR this season but apart from Gray, lack arms with significant upside on the current roster. In a division loaded with pitching, the Rockies will have difficulties matching up with the top arms on other clubs in their division. The Diamondbacks hold a clear edge.

San Diego Padres

Projected Rotation: Tyson Ross, James Shields, Andrew Cashner, Robbie Erlin, Colin Rea

Tyson Ross might be the most underrated starting pitcher in the league. The only qualified starter to post at least a 60 percent ground ball rate and strikeout more than a batter per inning, he gives the Padres a quality number one starter. “Big game” James Shields did not get the opportunity to pitch in many big games last season, and with his sudden drop in effectiveness, the Padres may not want him to have the ball in many this year. Was the drop in effectiveness due to aging and reduction in skills or was it an aberration? Projection systems forecast some positive regression for the righty who has a large range of potential outcomes in the 2016 season.

Perhaps best known as the pitcher the Padres acquired for Anthony Rizzo, Andrew Cashner has established himself as a steady number 2/3 starter. In spite of an inferior ERA last season, the hard-throwing righty has posted fWAR totals of at least 2.0 in each of the last three seasons. Robbie Erlin has spent a brief time in the majors in each of the last three years but appears to finally have the inside track to an extended look in 2016. The lefty lacks a put-away pitch and significant upside, but can eat some innings. Colin Rea, a mid-level prospect who held his own in a brief stint with the parent club last season, should round out the starting five.

2016 Steamer projections for the Padres' rotation are shown in the table below.

This is a solid group that could feature a dominant top three if Shields bounces back as expected. Ross is a stud who is projected to rival Greinke, while Ray and de la Rosa have similar outlooks to Erlin and Rea. Although the Padres have a slight edge over the Diamondbacks in projected fWAR, through three teams this is too close to call.

San Francisco Giants

Projected Rotation: Madison Bumgarner, Johnny Cueto, Jeff Samardzija, Jake Peavy, Matt Cain

Madison Bumgarner is a legitimate ace with a bulldog mentality that managers and teammates love. He wants the ball, puts the team on his back and can be counted on to come through when his team needs it most. He deserved every bit of his 2.93 ERA and 5.1 fWAR last season and is projected to post similar numbers this season. Recent signee Johnny Cueto brings significant upside to the staff, but inconsistencies down the stretch and questions about his elbow health drag him down. If he can stay healthy and return to his peak performance, the Giants could have the best 1-2 punch in the division.

Free agent acquisition Jeff Samardzija is a bit of an enigma: an ultra-talented pitcher with an oddly poor walk year with the White Sox. The Giants have a great history with pitchers and could help Samardzija return to his dominant 2014 levels, but like Cueto, there are risks involved.

MORE: The greatest Giants of all time, ranked 1 to 10

Questions abound in the rest of the Giants rotation, starting with Jake Peavy’s health and diminishing strikeout rate. He has posted at least 1.0 fWAR in every season since 2003, a streak he is barely projected to continue in the 2016 campaign. Matt Cain, formerly a part of a dynamic top-of-the-rotation duo with Tim Lincecum, has posted back-to-back injury plagued, sub-replacement level seasons. Steamer forecasts positive regression, and anything above replacement level seems like a win here. Chris Heston, a soft-tossing right-hander who enjoyed a solid rookie season, gives the Giants a nice depth piece.

2016 Steamer projections for the Giants' rotation are shown in the table below.

The Giants possess a top-heavy group with plenty of question marks. In a perfect world Cueto and Samardzija could rebound, Peavy and Cain could stay healthy and regain some of their past dominance, and Heston would build on his stellar 2015 season. The range of potential outcomes are enormous, but the upside is unmatched by Arizona or San Diego. The numbers are close, but I’ll take the wisdom of Dave Righetti and the upside of his new rotation members over the Padres and Diamondbacks.

Los Angeles Dodgers

Projected Rotation: Clayton Kershaw, Scott Kazmir, Brett Anderson, Hyun-jin Ryu, Alex Wood

Clayton Kershaw is the best pitcher in the division and the best pitcher in the league. The big lefty has posted at least 4.4 fWAR and an ERA below 2.80 in every season since 2009 and is an exceptionally strong bet to do so again. Rival aces Greinke, Ross and Bumgarner had great 2015 seasons and are projected to enjoy stellar 2016 campaigns as well, but all of the other pitchers in the NL West pale in comparison to Kershaw’s projected 2.08 ERA and whopping 7.4 fWAR.

After losing former co-ace Greinke in the eleventh hour to the rival Diamondbacks and backing out of a reported agreement with Hisashi Iwakuma, the Dodgers acquired veteran left-hander Scott Kazmir. The lefty has an unusual career path but after returning from a hiatus in independent ball, has posted at least 2.4 fWAR in each of the past three seasons. Ground-ball specialist Brett Anderson enjoyed a healthy and productive 2015. If he can remain healthy again, he will give the Dodgers another solid option in the middle of their rotation.

After missing the entire 2015 season with a shoulder injury, Hyun-jin Ryu is on track to return in 2016. If the lefty can make a full recovery, he will give the Dodgers significant upside in the middle of the rotation. A strong contender for the title of baseball’s most interesting delivery, Alex Wood is not a typical number five starter. In most other rotations the lefty would be slotted somewhere in the middle, but thanks to the Dodgers’ strong mid-rotation depth, he finds himself as arguably the best number five starter in the league. Brandon McCarthy is currently recovering from Tommy John surgery and is expected to factor in to the Dodgers’ rotation later in the season.

2016 Steamer projections for the Dodgers' rotation are shown in the table below.

In spite of the loss of Greinke, this is an extremely strong rotation featuring the best pitcher in the league and substantial depth throughout the starting five. Sound arguments could be made that each of the Dodgers’ current starting five have a true talent level of at least a number three starter. There are some health risks with Anderson, Ryu and McCarthy, and the status of all five starters as lefties is rather unusual, but the rewards far outweigh the risks. The Dodgers' rotation is unmatched at the front, deep in the middle and without weaknesses at the back. The Dodgers have the best rotation in the division.

Dan Weigel is a contributor at Sporting News focusing on pitching. Follow him on twitter at @DanWeigel38.