Clayton Kershaw's $215 Million Curveball

There are myriad reasons why Dodgers lefty Clayton Kershaw just earned a seven-year, $215 million contract extension, becoming the first player in history to pull in more than $30 million a season. Kershaw, 26 in March, boasts the fifth-best park-and-league-adjusted ERA (46 percent above average) ever for a starting pitcher during his first six seasons in the majors, trailing only Walter Johnson (164 ERA+), Mordecai Brown (158 ERA+), Smoky Joe Wood (152 ERA+) and Christy Mathewson (150 ERA+). He's a workhorse, having topped 200 innings pitched in each of the past four seasons, and he has fooled hitters like no other lefty (9.2 strikeouts per nine frames) this side of Randy Johnson (9.4 K/9) to start his career.

Yet for all of the breathtaking stats that Kershaw has compiled since making his debut at Chavez Ravine back in May of 2008, this one may be the most remarkable: he has thrown a total of 2,155 curveballs during the regular season, according to our Pitch F/X data, and exactly zero of those hooks have landed in the cheap seats. That's right -- Kershaw has never surrendered a regular-season homer on the pitch that earns him comparisons to Sandy Koufax. Batters have launched 1,945 home runs off curveballs dating back to '08, but nobody has gone deep against Public Enemy Number One.

What in the name of Vin Scully is going on here? How has Kershaw been so thoroughly dominant with his curveball, which has smothered hitters to the tune of a major league low .145 opponent slugging percentage from 2008-13? Here are three reasons why Kershaw's curve seemingly can't be taken deep.

Batters can't tell whether it's a ball or a strike -- or just don't think they can hit it

To go deep, you obviously have to swing the bat -- and opponents rarely do when Kershaw unleashes a curve. Batters have swung at just one-third of curveballs seen from Kershaw since '08, compared to the 40 percent major league average. Even when the pitch ends up being thrown in the strike zone, hitters pull the trigger less than half of the time (47 percent, compared to the 55 percent MLB average). Either batters can't discern whether it's over the plate in time to swing, or they figure it's futile to even try.

Hitters' swing rate by pitch location versus Kershaw's curveball, 2008-13

Kershaw's curve induces weak contact

When hitters do swing at Kershaw's curve, they often just pound the pitch into the infield grass or hit a weak fly ball. Kershaw has generated grounders 55.2 percent of the time that batters have put his curve in play, north of the 52 percent MLB average. Those who manage to loft the pitch into the air have won a moral victory, but little else. Batters have hit fly balls off Kershaw's curve an average of 244 feet -- second-lowest among all qualified starters dating back to 2008.

Lowest Average fly ball distance on curve balls put in play, 2008-2013 (min. 800 curveballs thrown)  

Kershaw can add and subtract with his curve

L.A.'s ace has thrown his curveball at an average of 73.4 MPH during his career. But he can dial it way up (topping 82 MPH on the gun) or way, way down (he threw a 49 MPH yakker to Yasmani Grandal on September 9, 2012 -- Grandal didn't swing, of course). That might be part of the reason why hitters so rarely swing at Kershaw's curve -- it could be a power pitch, or it might arrive at home plate slower than a Prius traveling on Interstate 5.

Kershaw was wild with curveball when he first arrived in the bigs, throwing it for a strike less than half of the time, but he has gradually learned to control the pitch (57 percent strike rate last year) while adding precision to his power arsenal. His curve, like the rest of his game, has only gotten better. That's a scary proposition any hitter dreaming of finally going yard off the pitch.

Newly-Extended Perez Must Improve Breaking Stuff to Take Next Step

The Texas Rangers have locked up yet another young left-handed starter, signing Martin Perez to a four-year, $12.5 million extension with three club options that could extend Perez's stay in the Lone Star State to 2020 and pad his pockets to the tune of $32.5 million.

A perennial top prospect, Perez erased memories of his rough big league stint in 2012 by posting a park-and-league-adjusted ERA that was 14 percent above average (114 ERA+). The 22-year-old enjoyed arguably the best rookie season ever for a Texas lefty, as only Mike Mason (114 ERA+ in 1984) matched him while throwing 120+ innings. Perez displayed sharp control (2.7 walks per nine innings) and racked up ground balls (47.9 percent of pitches put in play), both of which bode well for his future. But he also punched out just 6.1 batters per nine frames, far below the 7.2 average for starting pitchers in this strikeout-saturated era. To get more swings and misses, Perez will have to improve his pitch location with his breaking stuff.

Perez already has an out pitch in his changeup, which generated far more whiffs (39.7% of the time batters swing) than the league average (29.4%) and limited hard contact (.307 opponent slugging percentage, 90 points below the MLB average). His curveball and slider, on the other hand, induced swings and misses just 19% of the time (29.9% average for breaking pitches) and were frequently laced into the gaps (.437 slugging percentage, 92 points above the MLB average).

Why did hitters square up Perez's breaking pitches? The young lefty struggled to command his slider and curve, too often leaving breaking balls over the heart of the plate:

Perez's pitch location with his slider and curveball, 2013

Perez threw 29% of his sliders and curves to the vertical middle of the strike zone, third-highest among lefty starting pitchers in 2013. Belt-high breaking stuff tends to get clobbered, with hitters swinging through just 12.9% of sliders and curves thrown over the middle of the plate and slugging a collective .461. Perez was no exception, getting whiffs 13.8% of the time and allowing a .556 slugging percentage when tossing a belt-high breaking pitch.

The recent history of low-strikeout lefties who nonetheless posted quality ERAs during their rookie season is mixed. On the wildly positive side, Andy Pettitte pitched into his forties and cobbled together a career that may get him some Cooperstown consideration. However, the list of low-K lefties (six or fewer strikeouts per nine) with an ERA similiar to Perez (10-20 percent better than the league average) also includes the likes of Gustavo Chacin, John Lannan and John Halama. To be more like Pettitte and less like Halama, Perez needs to complement his knockout changeup with better-located breaking pitches.

Newly-Extended Rizzo Crushing Upper-Half Pitches

Anthony Rizzo is just 23 years old, but he has already beaten cancer and been traded twice. Learning to handle middle and high pitches, then, has been a cakewalk by comparison. Rizzo's staggering improvement against stuff thrown above the belt is a major reason why the Cubs felt comfortable locking him up with a seven-year, $41 contract extension, with two club options that could make it a nine-year, $73 million pact.

During his rookie year with the Padres in 2011, Rizzo's long, uppercut swing produced little more than wind power against pitches thrown in the upper half of the strike zone. The 6-foot-3, 240 pound prospect hit like a banjo-strumming middle infielder, with an upper-half slugging percentage (.217) that was over 200 points below the major league average (.425).

Rizzo's slugging percentage vs. upper-half pitches, 2011

In 2012, Rizzo made significant progress in solving his above-the-belt troubles. He cut his miss rate against upper-half pitches from about 32% to 13%, and he raised his slugging percentage to right around the league average (.415).

Rizzo's slugging percentage vs. upper-half pitches, 2012

Rizzo is making plenty of contact again on upper-half pitches this season (14% miss rate), but it's much louder contact. He's slugging .661 versus above-the-belt pitches, and his six homers on upper-half pitches already triples his 2012 total (two).

Rizzo's slugging percentage vs. upper-half pitches, 2013

Just two years after ranking in the bottom 20 among MLB hitters in upper-half slugging percentage, Anthony Rizzo now keeps company with the likes of Bryce Harper, Carlos Santana and Chris Davis in the top 20:

Highest slugging percentage vs. upper-half pitches, 2013

Rizzo's progress against middle and high pitches suggests that his new deal could be a bargain for the Cubs, and so do his career comps. Rizzo has a 122 OPS+ in 532 plate appearances during his age 22-23 seasons, a mark similar to those posted by first basemen like Willie McCovey, Keith Hernandez and Kent Hrbek at the same age.

It remains to be seen if Rizzo can match Stretch's feats of strength or get on base like Hernandez (to say nothing of growing such an awesome 'stache), but he's off to a great start.