Stats are great for reporting events, but when it comes to the raw tools and skills that drive those events, things quickly get trickier. When things that don't have a one-to-one relationship with a particular event, we need to use numbers in a more indirect fashion. The good news is that baseball is a data-rich game, so there are lot of numbers to work with when gauging tools or things on the major league level that border on the intangibles.
SPEED
Measuring a player's speed is difficult on multiple levels. First, there's no direct measure of straight-line speed in baseball. Even if you had every player in baseball run a 40-meter or 100-meter dash in spring training, it still wouldn't directly measure their baseball-relevant speed. Running the bases is a different activity than running to a line after hearing a starter's pistol.
But there are a number of ways to indirectly measure a player's speed: stolen base attempts/success, baserunning stats, triples percentage, outfield range, and GIDP as a percentage of grounders hit all give us an idea of a player's "baseball speed."
Bill James developed Speed Scores a few decades ago, and they tend to get the job done. I calculate my own Speed Scores as part of ZiPS, with a few other things, including adjustment for opportunity, age, longer-range looks than a single season, and even park effects. You might be scratching your head at how a park would affect speed, but beyond the playing field itself, parks that cause different styles of baseball have an effect on the stats that make up speed score. In the charts below, I'm not including pitchers.
TOP 10 (min. 50 MLB PA in 2016)
1. Jarrod Dyson, Royals
2. Socrates Brito, Diamondbacks
3. Raul Mondesi Jr., Royals
4. Trea Turner, Nationals
5. David Dahl, Rockies
6. Billy Hamilton, Reds
7. Mallex Smith, Braves
8. Dee Gordon, Marlins
9. Orlando Arcia, Brewers
10. Jemile Weeks, Padres
BOTTOM 10 (min. 50 MLB PA in 2016)
1. Peter O'Brien, Diamondbacks
2. Justin Bour, Marlins
3. Kevin Plawecki, Mets
4. Rene Rivera, Mets
5. Dae-Ho Lee, Mariners
6. Ryon Healy, A's
7. Prince Fielder, Rangers
8. Martin Maldonado, Brewers
9. Jett Bandy, Angels
10. David Ortiz, Red Sox