Can Jacoby Ellsbury bounce back after his nightmare 2015 season?

Jacoby Ellsbury has had better years than 2015. After getting off to a hot start, he tweaked his knee in late May, and was never quite the same after returning from injury. From his return on July 8th to the end of the season, Ellsbury put up a slash line of .224/.269/.332. During that stretch, he had just seven stolen bases in 11 attempts, only 19 extra base hits, and probably got hit with the Michael Jordan crying face photoshop at some point. With a yearly price tag of $23 million, Ellsbury will be on the hot seat if he cannot make an impact sooner rather than later.

Generally, athletes use a simple algorithm when discussing their health status with the media. If they are healthy, they say they are fine. If they are hurt but can still play, they say they are fine. For this reason, we can only speculate on exactly how healthy he really was after returning from his knee sprain. After whiffing at just 5.6% of pitches before his injury, Ellsbury's swinging strike rate jumped to 8.4% after July 8th. His average batted ball velocity also took a hit, dropping from 88.75 mph to just under 86 mph after getting hurt.

While we don't really know how to interpret exit velocity data yet, it should be noted that the Yankees used it to determine that Chase Headley had recovered fully from his back woes before trading for him in 2014. Owen Watson at Fox Sports also wrote that Ellsbury's plate discipline was worse after he hit the DL, which is almost never a good thing. According to Watson's article, the Yankees stated at some point that they found an issue with Ellsbury's leg kick, suggesting that inconsistent mechanics were hurting his timing.

But speaking of exit velocity, Ellsbury's numbers were interesting in more ways than one. Looking at Baseball Savant's batted ball velo leaderboard highlights just how bad things got. Out of 265 qualified hitters, Ellsbury ranked 237th with an average exit velocity of 88.36 mph on flyballs and line drives. Before that fateful day in May, flyballs and line drives left his bat at an average 90.35 mph, falling to 87.46 mph after his return. According to Fangraphs, his hard hit percentage and wRC+ were both abnormally low on liners and fly balls:

Unfortunately, league average hard hit rates on line drives and flyballs were not available, but Ellsbury clearly was not the same player in 2015. Even when Ellsbury did a good job of squaring up the ball, which was less often than usual, he wasn't hitting the ball as hard. We don't know what Ellsbury's batted ball velo numbers were like before 2015, but it is hard to believe that a player of his caliber has always had below average numbers in that department. What we can say is that Ellsbury probably never fully recovered from his injury, as there is good reason to believe that it spilled over into his peripheral stats.

All of this is to illustrate just how much had to go wrong for Ellsbury to have the disastrous season he had. In 2014, with slightly below average production on flyballs and line drives, Ellsbury was a four win player. Remember, that was a season which saw him leave his comfort zone and hit third for a solid chunk of the year. If Ellsbury has a even a remotely normal season in 2016, there is no reason to believe that he cannot be a spark plug at the top of the lineup. With regards to his health, Ellsbury has hinted that his injury is a thing of the past. He recently tweeted a video of himself doing an exercise that can't be fun for someone with a bum knee:

Do work pic.twitter.com/SlohYCSomR

— Jacoby Ellsbury (@JacobyEllsbury) January 15, 2016