If it seems like Odubel Herrera is making a highlight play in the outfield every day this year, that's not entirely true. According to our latest Statcast™ metrics, it's more like every third day -- and, at this admittedly early stage of the season, he's converting more difficult plays into outs than any other outfielder.
How do we know that? By looking at how far an outfielder was required to go to make a catch, and how much time he was given to get there from the pitcher's release, we can put a catch probability on each play. Because we know both of those inputs, we can take the eye test out of it -- two fielders who go the same distance in the same time will get the same credit, regardless if one had to dive or not.
By comparing those numbers across baseball since 2015, you can show how difficult a particular opportunity is to make. A chance with a 95-percent catch probability is made virtually every time. One with a 5-percent catch probability is just about never made, except in rare cases. As we broke down in our intro article, we've assigned ratings from "five star" to "zero star" for each difficulty level.

While it's fun to look at all catches -- as we did recently to show that the Cubs' outfield is off to a slow start -- it's more fun to look at the harder ones. That's what we'll do -- look at catches that received a three-star-or-higher rating. That is, the balls that are caught 75 percent of the time or less. While making a catch that's made 75 percent of the time may not sound impressive, remember that many balls to the outfield are extremely easy. Making a three-star catch is actually very impressive.

So, back to Herrera. Entering play Friday, 60 different outfielders had at least 10 opportunities to make a catch that would have had a 75-percent catch probability or below. Check out who's doing the best at converting those chances:
Highest conversion rate on catches with a three-star difficulty or higher
69 percent -- Herrera, Phillies
64 percent -- Max Kepler, Twins
63 percent -- Ender Inciarte, Braves
62 percent -- Lorenzo Cain, Royals
60 percent -- Kevin Kiermaier, Rays
58 percent -- Manuel Margot, Padres / Adam Duvall, Reds
57 percent -- Mookie Betts, Red Sox
56 percent -- Byron Buxton, Twins
53 percent -- Billy Hamilton, Reds / Jason Heyward, Cubs 
This is a list that's comprised of obvious defensive studs. Near the bottom are Jose Bautista, Melky Cabrera and Jonathan Jay. Everything about this makes sense.
For some comparisons, last year, Kiermaier led this list at 70 percent. Herrera was at 42 percent, still above average (which is 35 percent this year for qualified players). While still early in the season, it's one of the highest jumps.
What makes Herrera's improvement so interesting is that the first time most people probably heard his name was in 2015, when he helped finish off Cole Hamels' no-hitter by making a catch while falling down on the Wrigley Field warning track look extremely difficult. But this year, Herrera is making everything look easy. For example, here he is racing 88 feet in 4.6 seconds to rob Dansby Swanson on a ball that is caught only 14 percent of the time. Herrera doesn't even leave his feet to do it.

Now, compare that to Randal Grichuk's five-star rob of Heyward last year -- when he had to go 91 feet in 4.7 seconds -- from a nearly identical depth at a similar angle. Yet while Herrera got there easily, Grichuk had to lay out for a full dive.

Meanwhile, we have an example of a nearly identical 2015 play where outfielder Eury Perez -- in this case needing to go 89 feet in 4.7 seconds -- doesn't get there at all. It's a good comparison to show how effective Herrera has been.

Speed is king, when it comes to outfield range.
When we introduced our sprint speed metric earlier this year, we defined it as "feet per second in a fielder's fastest one-second window," and noted that last year, the range for qualified fielders was from 23 feet per second (very poor) to 30 feet per second (elite), with 27 being the average. Here, Herrera flashes great foot speed, getting up to an outstanding 29.4 feet per second to rob Giancarlo Stanton, covering enough ground so quickly that again, it doesn't even look hard.

So, is this a small sample blip or a real sign of improvement? It could be both. Not only is Statcast™ showing that Herrera has improved on these tough catches, but he already has +5 Defensive Runs Saved after totaling +6 for all of last season. Ultimate Zone Rating sees it similarly: +6 after being +4 in a full season in 2016.
Remember, improvement might be expected in this case. When Herrera was selected as a Rule 5 pick from Texas in December 2014, he'd been a career infielder. Though he played the outfield extensively in winter ball that year, his first full season as an outfielder was in the Majors with the Phillies in 2015.
Even now, it's been less than three full years since Herrera made the switch. Perhaps some inexperence was to be expected. Or perhaps, the Phils really saw something when they took him. And as they continue an impressive rebuild, they have one of the better center fielders to build around.