Diving catches, perfect throws -- defensive gems are some of the most exciting highlights. Here are some of the best of 2021, with help from Statcast.

Statcast's tracking can show us just how unlikely a great catch was in the outfield, or just how hard a throw was to nab a runner at the plate.

These are 15 of the top defensive plays of the season, with the numbers behind them.

Mookie Betts' game-ending catch, April 17
10% catch probability

We all know Betts is one of the best outfielders in the game. This was great even for him. With two outs in the bottom of the ninth inning against the rival Padres on April 17, the Dodgers center fielder raced into the gap and dove at full extension to rob Tommy Pham of a game-tying hit. His catch probability was just 10% -- Betts needed to cover 52 feet in just 3.3 seconds to make the play, getting a jump that was +8.6 feet above average. And he was pumped up.

Kevin Kiermaier's running catch at the wall, May 25
10% catch probability, 106-foot distance needed, 30.5 ft/sec sprint speed

Kiermaier runs like a deer in the outfield, and he went a long, long way to make this incredible grab against the Royals at Tropicana Field. Andrew Benintendi drove a ball deep into the left-center-field gap, and the Rays center fielder got on his horse, reaching a sprint speed of 30.5 ft/sec on his run to the wall (anything 30-plus is elite speed). Kiermaier needed to cover 106 feet in 5.1 seconds and contend with the fence to make the running catch, giving him a catch probability of just 10%. Left fielder Austin Meadows, who nearly collided with Kiermaier, would have needed to go only 90 feet in the same time, meaning it was a 65% catch probability for him. But Kiermaier's the one who got the ball.

Kiké Hernández's pair of 5-star plays, July 11
5% and 10% catch probabilities

Hernández used amazing jumps to make two five-star catches in back-to-back innings in center field for the Red Sox in this game against the Phillies at Fenway Park. A five-star catch means a catch probability of 25% or lower, Statcast's most difficult tier of play. On the first one, Hernández made a diving catch on J.T. Realmuto and turned it into a double play; his catch probability was just 5%, based on his 66-foot distance needed and 3.7 seconds of opportunity time. The next inning, he robbed Andrew McCutchen with another diving catch going the opposite direction; his catch probability on that one was 10%, as he needed to cover 57 feet in 3.5 seconds. Kiké's jump was +9.7 feet above average on the first catch and +8.0 feet above average on the second catch.

Kyle Tucker's World Series 5-star grab, Nov. 2
25% catch probability

With the Astros facing elimination in Game 6 of the World Series, Tucker started off the game with a 5-star catch in right field. Eddie Rosario, the very first batter, lined a ball toward the right-field line at Minute Maid Park, and Tucker got there despite a catch probability of just 25%. He needed to cover 43 feet in 3.2 seconds. It was the most difficult play of the 2021 postseason by catch probability, and the play was even bigger because of the stakes of the game.

Hunter Renfroe's rocket to the plate, June 9
98.0 mph arm strength

Renfroe has one of MLB's strongest outfield arms, and the Red Sox right fielder dialed up the hardest outfield assist of the season on June 9 against the Astros. Renfroe fired a 98.0 mph throw to the plate at Fenway Park to keep Alex Bregman from scoring in the first inning. Bregman was really hustling, too -- his 28.5 ft/sec sprint speed was way faster than his season average of 25.6 ft/sec (MLB average sprint speed, for reference, is 27 ft/sec).

Ronald Acuña Jr.'s strike to third base, June 20
97.3 mph arm strength

Just behind Renfroe's throw was this one from right field to third base by Acuña, just in time to catch Pete Alonso chugging first-to-third on Dom Smith's single. Alonso would have made it if not for Acuña's 97.3 mph arm strength and third baseman Austin Riley's perfect tag.

Joey Gallo's throw saves the game, May 13
97.3 mph arm strength

Just as hard as Acuña's throw and in a much bigger situation -- Gallo turned what would have been a walk-off sac fly by the Astros into an inning-ending double play. Houston had the bases loaded, one out and speedster Chas McCormick on third when Myles Straw lifted a 243-foot fly ball to right field. Gallo made the catch and, with McCormick tagging up and reaching a borderline-elite sprint speed of 29.9 ft/sec, made a perfect 97.3 mph throw to the plate.

Kevin Kiermaier keeps ALDS Game 4 tied, Oct. 11
90.0 mph arm strength

The hardest outfield assist this postseason went to Kiermaier, and his strike to third base came at a huge moment. The Rays were facing elimination in Game 4 at Fenway Park and had just rallied to tie the game in the top of the eighth inning. With one out in the bottom of the eighth, Alex Verdugo tried to get the go-ahead run to third base by tagging up on Hunter Renfroe's fly ball into right-center. But even though Kiermaier was moving away from third base when he made the catch, his throw was on the money and Yandy Díaz applied a perfect tag to keep the game tied into the ninth.

Brett Gardner's slide at the wall, April 10
127-foot distance needed, 29.5 ft/sec sprint speed

Gardner was in left field at The Trop when Brett Phillips drove a ball deep to the left-center-field wall. The longtime Yankee needed to cover 127 feet just to get to the ball, but even at age 37, he can still eat up ground in the outfield. Gardner reached a near-elite sprint speed of 29.5 ft/sec and made the catch sliding on the warning track, converting a catch probability of 30%.

Dylan Moore's run to foul ground, July 9
126-foot distance needed

Moore ran way over 100 feet to make this catch -- as an infielder. The Mariners second baseman was positioned straight up the middle when the Angels' Luis Rengifo popped a ball down the right-field line. Moore went all the way into foul ground at a 28.6 ft/sec sprint, converging with first baseman Ty France and right fielder Jake Bauers. The ball was in the air for 5.6 seconds. France needed to cover 93 feet to get there … Bauers needed to cover 125 … Moore needed to cover 126. He's the one who made the terrific sliding catch.

Gio Urshela goes into the dugout, Oct. 3
125-foot distance needed

It was Game 162, and the Yankees would clinch an AL Wild Card spot with a win. They were facing the rival (and division champion) Rays at Yankee Stadium, and the game was scoreless in the sixth inning. Austin Meadows popped a ball foul down the third-base line, and that's when Urshela made one of the best catches by an infielder all year. The only fielder on the left side in a shifted infield, Urshela had 6.1 seconds to cover the 125 feet from his position up the middle all the way to the Yankees dugout, where he made a beautiful basket catch -- and then went flying down the dugout steps, all while holding onto the ball.

Willy Adames' catch over the tarp, Oct. 9
111-foot distance needed

Here's another long running catch by an infielder, but in the playoffs. In Game 2 of the NLDS against the Braves in Milwaukee, Brewers shortstop Willy Adames covered 111 feet in 5.8 seconds on Ozzie Albies' popup down the third-base line to make a lunging catch going onto the tarp in foul territory.

Fernando Tatis Jr.'s rocket relay, July 6
95.8 mph arm strength, 0.62-second exchange

This might be the throw of the year by an infielder. With the Padres facing the Nationals at Petco Park, Tatis uncorked a remarkable relay to the plate to catch Starlin Castro in his attempt to score from first on Yan Gomes' double down the left-field line. As Castro rounded the bases, Jurickson Profar scooped up the ball in the left-field corner and hit Tatis as the cutoff man. Tatis took the throw, spun and fired a 95.8 mph strike to the plate, all in just 0.62 seconds. Getting rid of that strong of a throw, that fast ... wow.

Jorge Alfaro's cannon behind the plate, July 30
90.5 mph arm strength

Alfaro has always had one of the strongest arms behind the plate of any catcher, and he showed it here. This was the hardest throw on a caught stealing this season -- over 90 mph. And it wasn't just a cannon, it was perfectly accurate. Marlins shortstop Miguel Rojas caught the throw right in front of the second-base bag and Tyler Wade, despite his 28.8 ft/sec sprint speed, slid into the tag a split-second later.

J.T. Realmuto's quick strike, April 29
88.9 mph arm strength, 0.65-second exchange

Let's finish up with one more great throw by a catcher. Realmuto gets the ball down to second base as fast as anybody, and this play is a perfect example. The highest tracked arm strength on a caught stealing besides Alfaro's, Realmuto got rid of this 88.9 mph throw to second in under two-thirds of a second to catch Cardinals speedster Edmundo Sosa, who had a 29.3 ft/sec sprint speed trying to steal.