Brett Gardner was named the American League's Player of the Week on Monday for a week in which he went 13-for-25 (.520) with five doubles and a home run. Though he only made six starts, he got a hit in all seven of the Yankees' games over that week and collected seven hits in the final two games against the Mariners over the weekend. As a result of that outburst, Gardner has slipped past Robinson Cano for the team lead (pitchers included) in Baseball-Reference's Wins Above Replacement (bWAR) and is also the most valuable Yankee according to FanGraphs' version of WAR (he's still second to Cano in Baseball Prospectus's WARP). Obviously Gardner won't keep up his POTW pace, with its .545 batting average on balls in play, but can he be as valuable over the next three and a half to four months as he has been over the first two plus this season?
I think it's entirely possible that he could. To begin with, a great deal of Gardner's value comes from his play in the field. He's more valuable in center field, where he can make more plays, than in left field, and the Yankees revealed during Curtis Granderson's brief break between disabled list stays that they intend to leave Gardner in center even after Granderson's eventual return. So, there's no reason to expect Gardner's value in the field to decline.
On the other side of the ball, Gardner is hitting for significantly more power this year than he has in the past. His next home run will tie his single-season best, he's only six doubles shy of his previous best in that category, and he has four triples, half-way to his previous best well shy of the half-way point in the season. Projected over the remainder of the season, Gardner is on pace to reach triple digits in all three types of extra-base hits. Add those together, and his isolated slugging (slugging percentage minus batting average) is .169 compared to a previous career high of .110. That alone suggests that some correction is due.
However, Gardner has not been stealing bases at his typical pace or rate of success thus far this season. On the year, he's just 10 for 15, a 67 percent success rate and a pace for just 26 steals on the year. In his other two full seasons, 2010 and 2011, he averaged 48 steals per season at an aggregate success rate of 81 percent. However, since going just 1-for-3 in steals in his first 25 games, Gardner is 9-for-12 (75 percent) over his last 38 games, which is a 38-steal pace over a full season. That's a good indication that he has already reverted to something close to his prior form on the bases, and that the Yankees can expect more and possibly better going forward. Given that hitting for power and stealing bags are both ways to obtain extra bases, there's a good chance that Gardner's regression in the former category could be compensated for by his return to form in the latter.
On the season as a whole, Gardner's .339 BABIP isn't horribly out of line with his previous career mark of .319, but his walk and strikeout rates are both inferior to his previous career tendencies. Again, this suggests a possible balancing out that could keep the needle from moving on Gardner's overall production. A little less luck on balls in play but a few more walks would even out nicely. Indeed, his secondary average (which combines hitting for extra bases, stealing bases, and drawing walks) thus far this season is actually a bit below his career mark.
The upshot here is that Gardner isn't playing over his head. The exact form of his production is a bit different than what we're used to, but the net result is a player very similar in value to the one we saw prior to his lost 2012 season. In 2010 and 2011, Gardner was worth a combined 11.3 bWAR, or an average of 5.7 wins above replacement per season. At his current pace, Gardner would finish this season with 5.9 bWAR. He may be a small, funny looking, slap-hitter who will turn 30 before the season is over, but when he's healthy, Brett Gardner is a very valuable baseball player. That's something that has been true for far longer than the last week or even the last two months.