It’s been reported that the Mets, who have shown a reluctance to move veteran pieces under GM Sandy Alderson, could work out an extension with second baseman Daniel Murphy rather than trade him for prospects at this year’s deadline. The natural reaction to that news, particularly for Mets fans, is to wonder what an extension would cost the team.

Murphy entered the year with four years, 109 days of service time and a $5.7MM salary in his back pocket after avoiding arbitration with the team for the second time this past winter. He’s under control through next season and is due one more raise in arbitration before being scheduled to hit the open market for the first time in his career.

Using MLBTR’s Extension Tracker to look at extensions for second basemen with between four and six years of service time, Martin Prado jumps out as a strong comparable for Murphy both in terms of service time and in terms of production. Here’s a look at Murphy’s career to date alongside Prado’s career through the time he signed his four-year, $40MM deal with the D’Backs:

From an offensive standpoint, the two are very similar. Even when adjusting for ball park, Murphy has a 110 OPS+, where Prado’s was at 109 heading into the 2013 season. The big difference between the two, of course, is defense. Murphy, drafted as a third baseman, learned to play second base on the job and was a liability there early in his career. Defensive metrics have come around on his glovework at the keystone, but Defensive Runs Saved still pegs him as below-average, and Ultimate Zone Rating feels he’s average at best.

Prado, meanwhile, was considered a standout defender at third base and in left field at the time of his extension, and he was also capable of sliding over to second base or shortstop if needed. That’s versatility that Murphy simply doesn’t have to offer, and it’s a large reason for the fact that Fangraphs valued Prado’s career at 14.2 WAR when he signed his deal, while Murphy’s career to date is pegged at 11.1 fWAR.

However, Prado’s contract was signed 18 months ago, and his $4.75MM salary in 2012 was lower than Murphy’s current $5.7MM mark. It stands to reason that Murphy would earn more next season in arbitration than Prado would have in his final arb year, and we’ve seen the price of extensions grow over the past few seasons. Additionally, if the Mets feel that Murphy has progressed to the point where he’s at least an adequate defender at second base, they’ll likely be willing to pay for his future defensive value rather than ding him for his past struggles.

Murphy himself mentioned the possibility of a four-year deal multiple times in the report from Andy Martino of the New York Daily News, and if that’s the target window for an extension, something in the neighborhood of $9MM in 2015 and $12-13MM annually for his first three free agent seasons could work for both sides. That’d put his deal in the $45-48MM range over four years, beginning in 2015.

Murphy could also follow the route of Brett Gardner — another above-average player who was never seen as a star prior to his offseason contract extension. Gardner agreed to his final arbitration salary and then signed a four-year deal that began in 2015 and covered only free agent years. Were Murphy to go that route, an additional year at $12-14MM could be added to Murphy’s deal (which would then begin in 2016), meaning he would earn roughly $9MM in 2015 and earn something in the $48-52MM range for his age-31 through age-34 seasons (2016-19).