It’s the Year of the Strikeout in baseball, with career highs, records and milestones being reached seemingly every day. Whether it’s a result of higher fastball velocities, more eager-to-chase hitters or just better performance by pitchers, the numbers have reached astounding levels across the board.

All of that got us wondering: Who has the best strikeout pitch among starting pitchers?

We’ll use the stat "putaway rate" to determine our list. It's a simple concept that asks the question, “How often does a pitcher finish off a hitter with a specific pitch?”

The formula for it is: Strikeouts with pitch divided by two-strike pitches of that type thrown.

For example, if a pitcher records 50 strikeouts with his changeup and throws 200 changeups with two strikes, his putaway rate is 25 percent (50 divided by 200). It allows us to sum up who is the most effective and most efficient in one number.

From that, we can tell you that the top putaway pitch for a starting pitcher this season is ...

Corey Kluber, Cleveland Indians: Curveball (and slider)

Highest Putaway Rate Curveballs K Corey Kluber 39% 61 Trevor Cahill 34% 29 Charlie Morton 33% 34 Nate Karns 33% 36 Lance McCullers 32% 85

Kluber just broke the Indians record for consecutive games with at least 10 strikeouts, and it’s easy to see why. He has two outstanding “finish-you-off” pitches. His curveball has a putaway rate of 39 percent (61 strikeouts on 158 two-strike curves). But how does that translate into batting average? Opposing hitters are batting .099 (10-for-101) against the Kluber curveball this season.

Kluber’s slider -- or cutter, if you prefer -- comes in a couple mph harder. And though he doesn’t use it as often, it’s still netting him a 36 percent putaway rate, which ranks third on our list. In his past four starts, opponents are 3-for-35 with 12 strikeouts against it.

Put these two together with a pretty good fastball and his combination of pitches is downright nasty.

“Kluber is a master of manipulating the arc and velocity on three to four different looks of his slider and curveball,” a longtime scout said. “He has great touch and feel, and his pitches rarely stay in the strike zone. Rather, they’re late, sharp breakers that finish outside of the good hitting zones.”

Highest Putaway Rate Sliders K Max Scherzer 37% 77 Corey Kluber 36% 23 Carlos Martinez 35% 76 Carlos Carrasco 32% 35 Chris Sale 32% 71

This wasn’t No. 1 on the list, but it easily could have been. Scherzer’s mastery of opposing hitters starts with a fastball that hitters can’t square up, but it ends with a supremely nasty slider.

Scherzer throws two variants of it -- one with a late cut and the other with a sharp break -- and they’re both extraordinarily challenging to hit.

His putaway rate is 37 percent, the best for any starter’s slider. Opponents are hitting .081 against it (11-for-135) with 77 strikeouts.

Martinez has a great two-strike weapon with his slider -- and he knows it. He throws it 45 percent of the time with two strikes, which ranks seventh highest in the majors, but Martinez’s putaway rate (35 percent) exceeds each of the six pitchers above him on the list.

What makes the Martinez slider so tricky is it moves a lot in the last 20 feet leading up to home plate (4.4 inches toward the left-handed batter's box). That also ranks seventh among starting pitchers. Hitters often swing thinking the pitch will end up in one spot when the ball moves to another. In other words, this pitch makes hitters look bad.

Charlie Morton, Houston Astros: Curveball

Nate Karns, Kansas City Royals: Curveball

Surprise!

Bill James often says that a good stat will wow you, and seeing these pitchers rank as high as they do on this list qualifies. Cahill (34 percent), Morton (33 percent) and Karns (33 percent) rank 5-6-7 for best putaways. Cahill and Morton are fascinating because they’re late bloomers for the Cubs and Astros, respectively. Historically, they’re best known for getting ground balls, not strikeouts, but both seem to have found the magic touch.

The dominance of Karns’ curveball emerged as an incredible pitch during a three-start run earlier this season for the Royals in which he ramped up its usage, relying on it to record 24 of the 29 strikeouts he notched in 17⅓ innings of brilliance. But this might have come at a price. Karns suffered an elbow strain in mid-May and is on the 60-day disabled list. His return date is still not known.

Nelson has the second-highest putaway rate with any pitch with his curveball (38 percent), but the infrequency with which he uses it (he throws it about 10 percent of the time with two strikes) is only enough to land him as an honorable mention.

Dallas Keuchel might not be the traditional power pitcher, but he's finishing opposing hitters at a 29 percent putaway rate with his two-strike fastball. AP Photo/Kathy Willens

Common sense dictates that curveballs and sliders are going to rank at the top of these lists, given the movement and purpose of the pitch. But who ranks best among the other two primary pitch types?

Dallas Keuchel, Houston Astros: Fastball

Highest Putaway Rate Fastballs K Dallas Keuchel 29% 31 Robbie Ray 26% 69 Jacob deGrom 26% 72 Alex Wood 26% 38 Chris Sale 25% 82

Another one for the “whoa” files. Keuchel is best known as a ground ball pitcher, but in working the bottom of the strike zone (and below) so effectively, he’s able to rack up strikeouts as well. He doesn’t get to two strikes as often as some of the league's top power pitchers, but when he does, he’s able to finish (29 percent putaway rate) -- not just because he gets swings-and-misses, but because he gets called third strikes.

The average major league pitcher gets strike three on a taken two-strike fastball about 15 percent of the time. Keuchel is getting it at a 38 percent rate.

He has benefited in this way for years, previously from the catching of Jason Castro and now from Brian McCann.

Next up behind Keuchel are your more traditional power pitchers: Robbie Ray of the Diamondbacks and Jacob deGrom of the Mets.

Highest Putaway Rate Changeup K Johnny Cueto 28% 32 Danny Salazar 27% 39 Jacob deGrom 27% 17 Felix Hernandez 27% 17

It has been a rough go all season for Cueto, as his ERA stands at 4.26, well above last year’s 2.79. But Cueto still is able to get strikeouts with a changeup that has been the propellant pitch for much of his career success. His 28 percent changeup putaway rate ranks a smidge ahead of Cleveland's Danny Salazar.

Though the pitch has successfully finished off a good number of hitters, it has contributed to finishing Cueto off as well.

He has allowed four home runs on the 115 two-strike changeups he has thrown this season. That's as many as he allowed on the 1,149 two-strike changeups he threw in the previous eight years combined.

That teaches us something of importance here -- putaway doesn’t always equate perfection.