Diamondbacks offseason: 5 most pivotal players

[This is our first entry in the MLB Rotation, a project across the SB Nation baseball sites, where a common topic is discussed on all the sites on the same day. Check out the other entries around the system, for their takes on who their team's pivotal players might be.]

Must Keep - this player should not be discussed in any trade scenario
Paul Goldschmidt
I'm tempted just to write "Well, duh" and move on, but I don't think Goldschmidt's value can be overstated. Before this season, he signed an extension worth $32 million through 2017. Given a rough figure of one win above replacement being worth $5 million over that time, it means he has to provide 6.4 WAR over the course of the contract to justify the cost. According to fangraphs.com, Paul Goldschmidt in 2013 was worth... 6.4 WAR. So, job done there, I think. The NL MVP runner-up will cost Arizona $1.1m next year. He's the cheapest player to finish in the top two since 2006, when Ryan Howard won with less than one year of service time.

MLB Rotation: 5 pivotal players

We asked our SB Nation MLB team blogs to identify their team's five most pivotal players. Here's what they said.

Should Keep -- this player should only be discussed at the highest premium
Archie Bradley
The cliche is, there's no such thing as a pitching prospect, but when you get to the upper tier, that's not quite the case. Drays Bay did a study that looked at the subsequent value of prospects, and someone like Bradley, who was #7 on MLB's prospect list, and young for his level (not many 20-year-olds in Double-A), worked out as being worth $43.5 million above his costs, for the six years he's under team control. Another study on top 10 pitchers, had them contributing an average of 17.8 WAR over the same period. With not many open slots or gaping holes among our position players, it's hard to see a trade bringing that much in return for the D-backs.

Neutral -- this player is valuable to your team as-is but could also bring a nice return
Gerardo Parra.
Cue enraged shrieking from our nation's capital in 3...2...1... :) If we're going to trade from our stock of light-hitting outfielders with Gold Glove caliber defense, Parra might be the best bet. This is his second year of arbitration, and it isn't going to be long before he's s free agent. While his costs have been more than manageable so far - his 683 games have cost Arizona about $4 million - they are now beginning to escalate. His second Gold Glove and an increasing awareness of defensive value would probably mean a lot of interest, and with Eaton and Pollock to cover the ground, we might be better off with some power to protect Goldschmidt next year.

Should Trade -- your team should trade this player while there's still value
Aaron Hill
Despite an excellent 2012, and admitting that his value was curtailed by injury this season, Hill has averaged about two WAR per season over the past four years. That's fine, considering his total cost for that time was $20 million, but in 2014, he'll cost us $11 million, then $12m for each of the two seasons beyond that. Hill will be 32 by next Opening Day, and the hard fact is, second-basemen don't age well. Over the last seven seasons, the only players there aged 33 or more, even to put up 2.5 bWAR, are Chase Utley, Mark Ellis and Mark Grudzielanek. With Chris Owings looking a younger, much cheaper alternate, shifting Hill would free up a lot of payroll.

Must Get Rid Of -- Do whatever it takes
Heath Bell
The trade for Bell mystified me, and since his performance last season was basically replacement level (fWAR 0.0; nWAR -0.2), it's time for the team to admit the error and cut bait. Reliever volatility means that paying them the big bucks is always a dodgy proposition, and that's back-to-back years Bell has been close to worthless - he can't even blame Ozzie Guillen for 2013. Right now, there's a real chance Bell will not merely take up a bullpen spot, he'll also see (at least, initially) significant innings of work, while better pitchers are use for mop-up, or languish in the hell which is Reno. Given the margin we need to make up on LA, we can ill-afford any inefficiencies.