Carlos Gonzalez and Troy Tulowitzki are probably the best duo in the majors, but that hasn't translated into extended postseason success yet. In fact, they've made the playoffs together just once -- in 2009, when they lost the National League Championship Series to Philadelphia.
Over their last 1,400 innings or so, Arenado and Orioles third baseman Manny Machado have both been good enough to be considered the best defensive third basemen in the majors, but Arenado currently leads the league in defensive runs saved at the position. In fact, he has been the third best defender in the game -- behind Andrelton Simmons and Carlos Gomez -- according to the metric.
He has also put together the longest hitting streak in the majors this season and is just five games away from becoming just the 32nd player in baseball history to post a 30-game hitting streak. He extended his streak to 25 games on Monday with a home run in the second inning. He's hitting .311/.324/.492 this season with five home runs, 20 driven in, and leads all third basemen with six DRS.
The Rockies have surely considered a longterm extension for the 23-year-old. The Padres just signed second baseman Jedd Gyorko to a five-year deal worth $35 million, and Arenado has outplayed him in just about every way -- except hitting balls over fences, of course. Colorado would presumably have to top that figure, but it's a decent anchoring point for the club to use in negotiations. Gyorko is about a year-and-a-half older and is currently playing second, so it's far from a perfect comparison, but they have a similar amount of MLB service time and they finished sixth (Gyorko) and seventh (Arenado) in NL Rookie of the Year voting in 2013.
The sabermetric community would certainly prefer Arenado, as his glove makes him much more valuable than Gyorko, but the negotiations may not be steeped in UZR and DRS the way they might be if Dave Cameron was an agent.
The Rockies aren't a big market club, but they can hardly afford not to offer Arenado a favorable deal in order to keep him around for the rest of their run with Gonzalez and Tulowitzki.