Based on the success of my "MLB's 10 Most Effective Curveballs" article, I decided to look at the 10 most effective sliders this season.
I'm measuring slider effectiveness by Pitch Type Linear Weights, which says how many runs a pitcher prevents above average every time he throws 100 pitches.
So, if I say a slider's effectiveness is one run above average, that means that every 100 sliders that pitcher throws, he allows one run less than average.
I set two ground rules. First of all, pitchers have to have thrown at least 30 innings this year. Second, they have to use the slider at least 10 percent of the time.
For each pitcher, I'll list the average slider velocity, average slider movement relative to an average major league fastball (if you want to know why I'm comparing it to a fastball, just ask), slider usage (how often the pitcher throws the slider), and slider effectiveness (as measured by Pitch Type Linear Weights).
Also, just to clarify, this is me taking the leaderboard on slider effectiveness, listing the top 10 pitchers, and analyzing their sliders' success. This is NOT a subjective list.
So don't tell me I'm "leaving somebody off." It's just the leaders in the stat and my analysis for why they're leading.
Let's take a look. You'll never guess who's No. 1.
Slider Effectiveness: 3.91 runs above average
Slider Usage: 24.1 percent
Slider Velocity: 87.8 mph
Slider Movement: 9.8 inches right to left, 4.0 inches down
Cordero's slider is a knockout power pitch that can climb up to 91 mph. He's cut his use of the pitch significantly this year, and employs it as a two-strike chase pitch.
Since he doesn't have to worry about throwing strikes with it in that role, Cordero has gotten much more value from the slider.
Combined with his 93-97 mph fastball and killer changeup, the slider is a deadly weapon for Cordero.
Slider Effectiveness: 3.97 runs above average
Slider Usage: 26.5 percent
Slider Velocity: 87.8 mph
Slider Movement: 8.4 inches right to left, 7.5 inches down
Broxton's slider, like Cordero's, is a short breaker that goes as fast as some major league fastballs. Like Cordero, Broxton utilizes the pitch around a quarter of the time, most often as a swing-and-miss-for-strike-three pitch to end at-bats.
Batters have to look out for Broxton's 95-102 mph fastball, often leaving them helpless against the slider.
Slider Effectiveness: 3.98 runs above average
Slider Usage: 14.8 percent
Slider Velocity: 81.9 mph
Slider Movement: 6.2 inches left to right, 7.2 inches down
While Cordero and Broxton are hardly surprises on this list, Perkins starts a trend that will continue for most of the rest: a pitcher hardly noted for his slider actually excelling with it.
Perkins didn't even throw the pitch in 2007. He barely used it in 2008, and it was 2.22 runs BELOW average.
Yet this year, he's more than doubled his use of the slider, and it's become the second-best lefty slider in the game.
It's hard to tell exactly why Perkins is having so much success with the slider.
It may have something to do with the fact that he throws his fastball over 70 percent of the time. It's also possible that the scouting reports haven't been updated to reflect his increased use of the pitch, so hitters don't even know he throws it.
Time will tell if Perkins can continue this slider success.
Slider Effectiveness: 4.15 runs above average
Slider Usage: 25.1 percent
Slider Velocity: 77.6 mph
Slider Movement: 12.4 inches left to right, 8.3 inches down
Darren Oliver just edges out Glen Perkins for 2009's best lefty slider.
Who saw that coming? I sure didn't.
Oliver's worked on the slider since becoming a reliever in 2006, and he finally made it his primary secondary pitch this season, with spectacular results.
The pitch has a lot of side-to-side movement on it, and Oliver's stellar control also boosts the slider's value.
Slider Effectiveness: 4.18 runs above average
Slider Usage: 11.5 percent
Slider Velocity: 89.1 mph
Slider Movement: 6.9 inches right to left, 6.0 inches down
Chavez's slider regularly touches 90 mph and almost acts like a cutter. He uses his fastball and changeup more than the slider, so hitters don't look for it and get surprised by the late break and velocity.
Chavez's slider is a big reason why he's settled into the majors this year.
Slider Effectiveness: 4.52 runs above average
Slider Usage: 25.0 percent
Slider Velocity: 83.6
Slider Movement: 7.0 inches right to left, 8.5 inches down
Coffey's slider has a lot more late drop than most. Like the other righties on this list (Cordero, Broxton, Chavez) so far, Coffey has a mid-90s fastball that sets up the slider very well.
Coffey has been an excellent reliever this season, and the slider is a huge reason why.
Slider Effectiveness: 4.56 runs above average
Slider Usage: 26.5 percent
Slider Velocity: 83.3 mph
Slider Movement: 11.4 inches right to left, 11.6 inches down
Here's an interesting case.
Gutierrez didn't even throw a slider prior to this year.
Now, he's got one of the most effective sliders in baseball.
Looking at that movement, it's not hard to see why.
The pitch has a ton of movement down and away from righties, and is also set up by a hard mid-90s fastball.
The excellent slider is no fluke with that sort of movement, and should allow Gutierrez to be an effective reliever for years to come.
Slider Effectiveness: 4.90 runs above average
Slider Usage: 44.4 percent
Slider Velocity: 83.4 mph
Slider Movement: 11.2 inches right to left, 6.9 inches down
Gregerson throws a sweeping slider that breaks far more horizontally than vertically.
His success with the pitch is very striking. This is for two reasons.
First, Gregerson throws the pitch nearly half the time, so hitters know it's coming.
Second, he doesn't have a big fastball to set it up with, working in the 88-93 mph range with the fastball.
However, the late horizontal movement on Gregerson's slider is obviously fooling a ton of hitters, and there's little reason to think he and the slider won't keeping sending hitters back to the dugout empty-handed.
Slider Effectiveness: 5.03 runs above average
Slider Usage: 30.7 percent
Slider Velocity: 84.5 mph
Slider Movement: 6.4 inches right to left, 6.3 inches down
One of the few pitchers on this list who doesn't come as a surprise, Street has absolutely dominated hitters this season, with his slider coming in as his best pitch.
It doesn't have incredible movement, but the slider is aided by Street's deceptive delivery and arm angle.
It has long been a very effective pitch, and Street's slider should keep hitters shaking their heads for years to come.
Slider Effectiveness: 5.44 runs above average
Slider Usage: 15.0 percent
Slider Velocity: 85.1 mph
Slider Movement: 9.2 inches right to left, 3.3 inches down
I'm just as shocked as you are.
Virgil Vasquez, Pittsburgh's emergency fifth starter, has the best slider in the game?
Vasquez's fastball, curve, and changeup have all been hit hard this year, but somehow, his slider has dominated opposing hitters.
For what it's worth, scouting reports do tend to say the slider is the righty's best pitch, and it does have good lateral movement.
Perhaps Vasquez's slider's success is a fluke, and perhaps it's not. It'll be interesting to see what happens with it if and when he gets called back to the majors.