After a hot start to the season that featured an eleven-game winning streak, the Mets have hit a rut. The offense has been the primary culprit, as injuries to David Wright and Travis d'Arnaud and struggles from several other regulars have conspired to drain the Mets of nearly all of their offensive fire power. Unsuprisingly, that has people looking for logical trade targets, and many have again set their sights on Troy Tulowitzki.
On the surface, the fit makes sense. When healthy, Tulowitzki is one of the best players in the game and has been the second best shortstop in baseball by fWAR since his full season debut in 2007—Hanley Ramirez edges him out slightly, partly because he has 700 more plate appearances. The Mets, on the other hand, are relying on the combination of okay offense and very bad defense offered by Wilmer Flores.
But a trade for Tulowitzki would be huge mistake for the Mets. Concerns about his health and performance are nothing new, and with a quarter season of data to analyze after his hip surgery last season, trading for him now seems even less appealing.
First, there's his offense. Though he's not a hyper-patient hitter in the mold of Joey Votto or Jose Bautista, Tulowitzki has always sported a decent walk rate, with a career mark of 9.9%. Combined with his strong batting average (and some help from Coors Field BABIP), this has helped give him a career .371 OBP. Digging more deeply into his plate discipline numbers, Tulowitzki has always posted below average marks for O-Swing% (percent of pitches swung at outside of the zone), Z-Swing% (percent of pitches swung at inside the zone), and total swing rate, while posting above average O-Contact%, Z-Contact%, and total Contact% marks. In other words, Tulowitzki has always been more selective than average and better at making contact when he does swing.
Here's a graphical representation of how Tulowitzki's career rates compare to the 2015 data:
Tulowitzki is swinging more, especially outside of the zone, and making less contact when he does. As such, his walk rate has plummeted to a paltry 2.2%, while his strikeout rate has risen to 22.2%. It's only 158 plate appearances, but walk rate typically stabilizes after 120 plate appearances, contact rate after 100, and swing rate after only 50 plate appearances. All of these stats are reasonable descriptions of 2015 Troy Tulowitzki given the sample size, and they don't paint a pretty picture. Note that this simply means what we've seen so far is real, not that this is going to be the new norm.
Tulowitzki's power is also down significantly, as his .143 ISO is well below his career average of .216. This can easily be explained by the distance of his fly balls and home runs, which has declined over the past few years. Some relatively new work from Alex Chamberlain at Fangraphs indicates that Tulowitzki's ISO is significantly below his xISO—which predicts ISO based on Pull%, Hard%, and FB%—so there is some hope that the power can come back. Fly ball distance, however, has usually been the best indicator of ISO, and Tulowitzki's power outage has come with a significant drop in batted ball distance, a concerning underlying reality.
The story isn't any better on the defensive side of the ball. Ignoring UZR and DRS numbers for this season due to the small sample size, Tulowitzki's 2015 Inside Edge fielding metrics indicate he's making both regular and difficult plays at short less often than he has in the past. Tulowitzki has only been slightly better than Wilmer Flores in that regard this season.
It's not outlandish to project that Tulowitzki will have to move off shortstop, one of the more demanding positions on the field, as he ages. The Mets could theoretically slide Tulowitzki to second base or the outfield, but doing so would sap some of his value.
Consideration must also be given to Tulowitzki's extensive injury history, particularly as he comes back from a labral repair in the offseason. The injury that originally put Tulowitzki on the disabled list in 2014 was a quadriceps injury, which the Rockies doctors then determined was caused by instability in his leg due to the damage in his labrum. That Tulowitzki had his quad flare up recently is cause for concern.
So far this year, Tulowitzki has not been a good player, and it hasn't just been bad luck. But it is just one quarter of a season, and these trends might be little more than a statistical fluke. It's possible that Tulowitzki is simply not fully recovered from his hip surgery—full recovery time is often listed as six months, but regaining full functionality, range of motion, and strength can take longer. In any case, it's unlikely that a top five player has turned into a below-average one overnight.
How much he rebounds is an entirely different question. Will he ever be the offensive force he's been for the better part of the last decade again? Regressing his 2015 statistics back towards his career averages still winds up with a solid player, just not the elite, all-around talent that he has been. But given the contract, injury risk, declining production, and the cost in prospects, acquiring Tulowitzki isn't a good move.