Just a few months ago, the Yankees could have had Brandon Phillips in exchange for Brett Gardner, a move that could have made sense given the absence of Robinson Cano. They instead rejected that offer and gave Gardner a four-year, $52 million extension. The sentiment among many Yankee fans was that this contract was a bit too much for just an average player, an everyday regular but not a star. But at one quarter of the way through the season, Gardner is certainly playing like an All-Star. For the Yankees, he's not only playing up to his contract, but beyond it. And while the payout does not begin until next season, Gardner is proving that the extension was well-deserved.
For someone who watches Brett Gardner every day, he does not look All-Star caliber. He is certainly batting at a decent clip, .304/.379/.424 (125 wRC+), but that can be easily dismissed because his BABIP of .405 is sure to regress to his career number of around .330. I do not believe Gardner to have a true .300 batting average, and most projection systems (ZiPS and Steamer) agree that he will fall between .270 and .280 by season's end. That could leave him with a wRC+ that settles between 98 and 113, which would be decent, but more than respectable given that his value is mostly derived from base running and defense.
Gardner's base running has been considered conservative in recent memory, but he's certainly been more aggressive this season so far. Gardner has already stolen 11 bases, and has not been caught stealing yet. He has been more aggressive than last season, but also more efficient and careful in choosing his stolen base opportunities. His current base running pegs him at 3.0 base running runs above average (the FanGraphs measure), his highest mark since 2011.
And how has his transition to left field gone? It appears that it has worked out as planned. According to both UZR and Total Zone, Gardner is much more competent in left field. Total Zone had Gardner at 54 runs above average as opposed to -9 for center field (going into the season), and UZR has Gardner at 35.2 UZR/150 for left field against 11.3 in center. By making the move, he has become more effective given his positional adjustment. While defensive data does not say much this early in the season, his past performance in the outfield is certainly an indicator that his success will continue. And according to Inside Edge Fielding Data (which helps create UZR), Gardner has fielded 100% of the unlikely, even, and routine-type plays while making 85.7% of plays that were deemed likely to be made. This is definitely a small sample, but his defense has been more than competent so far.
So far, all calculations of WAR say that Brett Gardner is having an excellent season. FanGraphs has said that he has accumulated 1.8 WAR and ZiPS and Steamer say that number could finish up to 3.7-4.4. PECOTA has said he is worth 1.6 WARP and will likely finish the season near 3.8; Baseball-Reference claims that he has accumulated 2.0 WAR already. By all accounts, this would be one of Gardner's best seasons in his career, depending on which measure you use to analyze him. Given that the market rate for a win is worth approximately $7 million and he could be worth about four wins, he could produce up to $28 million in a year in which he is only being paid $5.6 million. While he will not have the same abilities in the last year of his extension, one more year like this one could make that contract a huge bargain.