On Monday, we saw our first two Five-Star Plays of the 2017 season. In Minnesota, Byron Buxton made the first of what we expect will be many spectacular plays this year, robbing Alex Gordon. While in Baltimore, Jose Bautista made taking a hit away from Joey Rickard part of an impressive Opening Day. Since we had nearly 300 Five-Star Plays in 2016, these ought to be just the first of many.
But it's fair to note that not all plays are created equally, because Catch Probability is mainly looking at how far a fielder needed to go and how much time he had to get there. If Buxton had been positioned so that he had to go only 10 feet in 2.9 seconds rather than the 36 feet it really required, then that same Gordon batted ball wouldn't have been an outstanding play, it would have been an easy one. It wouldn't have been Five Stars. It would have barely rated at all. Positioning matters.
While it's very difficult to determine whether the fielder or his coaches deserve credit for positioning, that's something that came up last week, when we used our newest Statcast™ tools to check out which outfielders added the most value in 2016. We combined frequency of catches made with the difficulty of each of those plays, and unsurprisingly, names like Mookie Betts and Billy Hamilton rated very highly.
We did note, however, that Tampa Bay's elite Kevin Kiermaier, despite leading all outfielders in percentage of catches made, was a little lower than expected when difficulty was rolled in because he "had, on average, the least difficult batted balls in baseball coming his way." Great as Kiermaier may be -- and he is -- even he can't turn a lazy fly ball into something that requires Five-Star skill. Opportunity matters too, and much of that is out of an outfielder's hands.

That's positioning, sure, but also how many balls a pitching staff puts in play (the Twins allowed nearly 700 more non-homer batted balls than the Cubs, for example), and also the types of balls those are (the Braves' staff allowed an average exit velocity more than 2 mph higher than the Dodgers did). Great fielders make the plays they can get to, but how do we know what kind of plays they're getting?
If we can assign credit for the plays that are made, we can do the same thing for the opportunities that come too, and answer what's actually an important question: Who got the most chances to do something great? Or the fewest? Who added the most value over what came their way?
If we look at the 128 outfielders with 100 catch opportunities in 2016, you can immediately see what we meant by Kiermaier. No outfielder found himself with "easier" batted balls coming his way.
Estimated Catch Probability of balls hit to outfielder in 2016
89 percent -- Kiermaier, Rays
88 percent -- Joc Pederson, Dodgers
88 percent -- Hernan Perez, Brewers
88 percent -- Scott Schebler, Reds
88 percent -- Mark Trumbo, Orioles
The Major League average is 83 percent, and the spread there goes down to 73 percent, which is to say that the Phillies' Tyler Goeddel had, on average, the most difficult balls in play hit to him. If you're wondering why these numbers feel so high, realize that the distribution of balls is such that a huge majority of catches are relatively easy -- nearly over four-fifths of catches have a Catch Probability of 75 percent or higher.
Put another way, six outfielders, led by Jackie Bradley Jr. at 44, had at least 40 Five-Star opportunities. Ender Inciarte and Adam Eaton each converted 10 of those extremely difficult plays into outs -- Kiermaier, meanwhile, had only 10 opportunities all season long. It's fair to note that he missed several weeks due to a hand injury, yet the fact remains.

On a rate basis, only 3.6 percent of balls that went Kiermaier's way were Five-Star opportunities, the lowest of anyone in our group of 128. The average in our sample was 8.2 percent, and at the high end, Jake Marisnick had 16.1 percent of his balls qualify as being Five-Star, and Goeddel had 19.6 percent. It's true that Goeddel saw more difficult batted balls than any outfielder, but it's also true he was unable to convert even a single great play.
If we can see how difficult the opportunities were, and how difficult the catches made actually were, then we can also see what the differences between the two were. Josh Reddick, for example, had balls hit his way with an average Catch Probability of 87 percent, and the catches he made had an average probability of 87 percent, so he did more or less what was expected. At the other end of the scale, for example, Matt Kemp had balls hit his way that averaged to 82 percent, and the catches he made averaged 75 percent, so his teams lost value there. 
Added Catch Probability value of balls hit to outfielder in 2016
+9 percent -- Hamilton, Reds
+8 percent -- Desmond Jennings, Rays
+7 percent -- Marisnick, Astros
+7 percent -- Inciarte, Braves
+7 percent -- Keon Broxton, Brewers
+7 percent -- Juan Lagares, Mets
With the exception of Jennings, these are all the names you'd expect to see, particularly Hamilton, who is baseball's foremost highlight reel. The next two names on this list are Betts and Jason Heyward (+6 percent each) and then Kiermaier at +5 percent, tied in a group that includes Buxton, Eaton and Travis Jankowski. You can always add value, no matter how it's presented to you.

This was all a similar story in 2015, where Kiermaier had 6.1 percent of the catchable balls that came his way be classified as "Five-Star," one of the eight lowest marks in the bigs. One of the few lower than him was Brandon Guyer (5.6 percent), who was then a Tampa Bay teammate. Is it possible the Rays are onto something with the way they position their outfielders? Or are Tampa Bay's pitchers just generating fewer difficult balls in the first place?
We're still learning the answers to those questions. The Rays allowed 210 homers last year, the sixth most in baseball, and they had the 11th-most non-grounder batted balls hit at over 95 mph, which doesn't strongly support the idea of an elite soft-contact staff. But in our extremely preliminary look at positioning data, Kiermaier's average start position of being 63 feet away from balls hit to him is approximately the league average.
So we don't know why -- at least not yet. But we do know that Kiermaier vacuums up anything and everything that comes to him, unlike any outfielder. It just so happened that last year, there weren't quite so many balls hit his way that required his amazing skills. It might be bad luck. It might be pitching. It might be positioning. We're excited to learn more.