How Tulowitzki was (and wasn't) affected by Coors
Rockies hitters' launch angles 3 degrees lower at home than away
There's not a single team in any of the four major American team sports that's been waiting to get back to the playoffs longer than the Toronto Blue Jays, which is a large part of why the decision to truly go for it by adding Troy Tulowitzki was so exciting. The Blue Jays' new shortstop won't solve their pitching problems, but he's clearly an upgrade on both sides of the ball over the departed Jose Reyes.
The biggest question that follows Tulowitzki to Toronto is how the injury-prone shortstop will hold up on the unforgiving turf at Rogers Centre, but he's also going to have to overcome the same uncertainty that any hitter leaving Coors Field has to deal with: What kind of bat will he be away from the friendly Mile High City? Let's use Statcast™ to investigate.
Over the past three seasons, Tulowitzki has indeed been a more effective offensive performer at home, putting up a 151 Weight Runs Created Plus that makes him 51 percent better than a league average hitter. Of course, the 129 wRC+ he's had on the road is still excellent, and would by itself make him a more effective hitter than any other shortstop in the same time frame who still plays the position today. There's no doubt that some hitters have had successful careers only because they called Coors home, but for a certain caliber of hitter -- Matt Holliday comes to mind -- there's still plenty of damage to be done after leaving Colorado. (There's some convincing evidence that playing home games in Denver causes Rockies hitters to then do worse on the road than they may have otherwise.)
For Tulowitzki and the rest of the 2015 Rockies, what's particularly interesting isn't the outcome of the balls in play so much as the angle that they come off the bat. We ran some numbers on launch angle, which can generally be read as zero degrees being a ball hit directly back at the pitcher's release point. Negative numbers would be grounders or low liners, positive numbers would be high liners or flies. What we learned is that the launch angle for hitters playing in Colorado, no matter which team, tends to be lower than in the average ballpark.
Rockies hitters in Colorado: 7.77 degrees
Opposing hitters in Colorado: 6.13 degrees
Rockies hitters on the road: 10.75 degrees
MLB average: 10.28 degrees
Tulowitzki falls in line with the trend, having a launch angle of 7.97 degrees at home and 10.74 degrees away. (As expected, his average batted-ball distance of 221.2 feet on the road is less than his 236.5 feet at home.) Clearly, the ball comes off the bat lower in Colorado, which might not be what you'd expect when you envision endless mile-high homers.
So, what's causing that? For now, we have hypotheses, and while that's not the same thing as hard, solid evidence, that's sort of the point -- Statcast™ is raising questions we could never consider before. One theory is that pitchers, wary of the lack of movement on their breaking pitches in the thin air, avoid them to focus on more fastballs. (For example, Colorado starter Jorge De La Rosa uses his curve 8.8 percent of the time on the road, and only 2.0 percent of the time at home.) Those fastballs are generally sinking or thrown low to get grounders, and indeed the Rockies are second this year in ground-ball percentage at home and fourth since 2002 in overall pitching grounder percentage.
That seems to be based less by what happens to the ball when pitched and more by the conscious effort of teams to avoid what might happen, in that throwing low fastballs has long been the strategy. It's also possible that in addition to teams trying for grounders, those additional low fastballs are easier to put solid contact on that breaking pitches, thus leading to more low line drive, though that's difficult to quantify without accounting for the talent of the pitchers involved, as well.
As for Tulowitzki, it will be interesting to see if his launch angle changes during his time in Toronto. Either way, Jays fans won't have to worry about his production. As long as Tulowitzki is healthy, he's the best all-around shortstop in baseball no matter what city, state or country he's in.