After a slow start, Brett Gardner is hot. He's now hitting .247/.356/.461, 26%/14% K/BB, 130 wRC+. His defense is still strong, and Gardner has hit a bunch of clutch home runs. The Yankees are in first place, a full 4 games up on the Red Sox.
I think the Yankees should start thinking about trading Brett Gardner in the early summer, assuming nothing changes (the Yankees are in a similar position, Gardner and the players I'm about to mention are all hitting about the same). Here's why:
1. The Yankees have a major logjam in the outfield
Between Triple-A and the majors, the Yankees currently have Brett Gardner, Aaron Hicks, Jacoby Ellsbury, Aaron Judge, Clint Frazier, Dustin Fowler, and Mason Williams (plus Tyler Wade). With the exception of Mason Williams, everyone is playing at the top of their game right now. Aaron Judge isn't going anywhere. Hicks is having a great season. Frazier and Fowler are both incredibly talented and playing great. Jacoby Ellsbury is still untradeable, although he's doing better as well.
Brett Gardner is the past, these guys are the future. With Aaron Judge and Jacoby Ellsbury locked in for some time, the Yankees will have to make room eventually. Moving Gardner is the only real way to open spots.
2. Gardner Could Return Value Right Now
Several contending major league teams would benefit from adding Brett Gardner. Washington just lost Adam Eaton for the season without an above-replacement level reserve player in center field. Pittsburgh, San Francisco, St. Louis, Detroit, and others would consider Gardner an upgrade. His contract is affordable and limited. Gardner could bring real assets in return.
What kind of assets? Given that the Yankees are contending, they wouldn't want to make their team worse in a trade (more on that later). While I would love to see Juan Soto come back in return, the Yankees could instead ask for starting pitching, relief help, or a first baseman better than Chris Carter. For example, the Nationals have and do not need Adam Lind, and may be willing to talk about Joe Ross. A three way trade is also a possibility.
This may also be the final opportunity for the Yankees to get value for Gardner. If he slumps, his trade value will disappear, and the Yankees will have further difficulty resolving their long term log jam.
3. The Yankees Wouldn't Be All That Worse Off Without Gardner
This is probably the controversial part. Brett Gardner is off to a great start, but how good is he really? Gardner has been a very consistent, if slightly declining, player over the past four seasons, worth 3.4, 3.5, 2.6 and 2.4 fWAR. His strikeout rate has increased dramatically in 2017. I think that it's plausible that Gardner is going to be a 3 win player this season, but it seems very unlikely that he will maintain his current performance. The Yankees can replace (and possibly improve upon) 3 WAR.
Aaron Hicks would immediately receive the bulk of Gardner's playing time. Hicks is beginning stages of what may be a major breakout season. He's hitting .316/.444/.632 with a crazy 12%/19% K/BB and 197 wRC+. Better yet, he has room to improve on his .295 BABIP. Hicks is younger and has similar defensive skills as Gardner. While Hicks has mostly struggled at the major league level, his minor league numbers suggest that these skills existed before 2017. Hicks may or may not be better than a 3-win player, but he's probably not much of a step down at this point.
Frazier and Fowler are also potential upgrades. Frazier is hitting .256/.360/.489 at Triple-A, is one of the top outfield prospects in all of baseball, and has the physical tools to be even better. Fowler, who BA has #1 on their hot sheet right now, is hitting .297/.343/.545 and playing excellent defense in center. There is a good chance that both are upgrades on Gardner this season, and at least one figures to be in the long term picture for the Yankees.
The key point: what is the probability that Brett Gardner will be better in 2017 than all three of Fowler, Frazier, and Hicks? I think it's less than 50%. One of the three is just as likely to break out as Brett Gardner is to regress to his previous career trajectory. All three probably have higher ceilings than Gardner, meaning the Yankees could miss out on an opportunity to upgrade by playing it safe with Gardner.
I love Gardner. He's one of the last remaining links to the 'Core Four' era of Yankees. I remember covering him in the minor leagues years ago. But the Yankees could benefit from using him to strengthen other parts of their team right now.