How Adding a Slider Could Take Stephen Strasburg to the Next Level

Adam Wells@adamwells1985Featured ColumnistFebruary 19, 2014

Washington Nationals starting pitcher Stephen Strasburg delivers a pitch against the Miami Marlins during the fifth inning of their baseball game at Nationals Park in Washington, Sunday, Sept. 22, 2013. Strasburg got his 500th career strikeout during the game. (AP Photo/Susan Walsh)
Susan Walsh/Associated Press

For a pitcher who already throws a fastball that can touch 100 mph when it's not breaking bats thanks to heavy sink, a curveball with such hard snap that it can break legs and a changeup that makes angels cry, adding another pitch to the arsenal might seem like overkill. 

For Washington Nationals ace Stephen Strasburg, enhancing his already-deep arsenal does serve a clear purpose. 

Adam Kilgore of The Washington Post reported that a point of emphasis for Strasburg during spring training is the addition of a slider that he apparently started toying with during the offseason. 

In his fifth professional season and more than three years removed from Tommy John surgery, Strasburg has a reached a point at which he feels comfortable building off his current, considerable arsenal. Along with his fastball, curve and changeup, Strasburg is working to add a slider.

Even though he may not have been as dominant as people would have liked in 2013, Strasburg was still one of the best starters in baseball. He ranked in the top 10 in strikeouts per nine innings (9.39), strikeout percentage (26.1), batting average against (.205), WHIP (1.05), ground-ball percentage (51.5) and expected fielding independent ERA (3.15) among starters with at least 180 innings pitched. 

Despite that dominance, Strasburg left fans and analysts wanting more. He was hyped as the greatest pitching prospect in history when the Nationals made him the No. 1 pick in 2009 and dazzled as a rookie in 2010 before needing Tommy John surgery. 

Upon returning at full strength in 2012, Strasburg looked like he was going to be in the spot where Clayton Kershaw is now. Strasburg posted 4.1 FanGraphs' Wins Above Replacement, 197 strikeouts and a 3.16 ERA in 159.1 innings before the Nationals shut him down. 

David Schoenfield of declared last August that Strasburg hadn't yet reached "ace" status. 

Despite all those positives, I can't classify Strasburg as an ace just yet, although we all have various definitions of what that means. The goal for starters is to prevent runs and pitch deep into games. He ranks 22nd among MLB starters in ERA and lower if you look at runs per nine innings since he's allowed nine unearned runs. He's also just 41st in innings pitched -- 42 innings fewer than Kershaw, not that any pitcher compares favorably to Kershaw these days.

This brings us to the one major flaw in Strasburg's game and back to the slider's importance for him to take that necessary final step toward greatness. 

Just looking at Strasburg's career numbers, it can be hard to find anything wrong. He's allowed 466 baserunners (343 hits, 123 walks) with 504 strikeouts in 434.1 innings. But he's not perfect. 

Strasburg had problems getting lefties out with his fastball. Take a look at some of these numbers from last season.

Stephen Strasburg vs. LHH, 2013

As you can see, Strasburg's changeup and curveball are murder on left-handed hitting. But the results against his four-seamer and especially the sinker are a cause for concern. 

Since his sinker is thrown at a slightly lower velocity than the fastball and moves away from lefties (into the barrel of their bat), it's easier for them to drive the pitch. The numbers back that up, clearly. 

The addition of a slider serves two purposes for Strasburg. First, it just makes his arsenal deeper and creates more problems for opponents, who now have to plan for a pitch they've never seen him throw. 

Second, and more importantly, it gives Strasburg a true weapon against left-handed pitching to complement his changeup. His curveball has also been effective against them, but the slider can be thrown with more velocity and at their back foot. 

Implementing the slider will allow Strasburg to use it and the four-seamer as his primary weapons against left-handed hitting. He can then focus on being more fastball-changeup heavy to right-handed hitters, with the curveball and sinker sprinkled in. 

Honestly, Strasburg's fastball gets such good natural movement that he could probably ditch the sinker altogether without any real consequences. 

Stephen Strasburg's Horizontal Pitch Movement, 2013
PitchAvg. Velocity (MPH)Movement (Inches)

Randy Johnson's career took off after he learned to throw a slider, because it gave him a true weapon to neutralize right-handed hitters. 

Another factor of Strasburg using the slider, which The New York Times' Tyler Kepner pointed out in a piece about Johnson nine years ago, is the way it can help clean up a pitcher's mechanics. 

Johnson's slider also makes his fastball better. In his early years, when the fastball sailed too high, (former Seattle catcher Scott) Bradley would call for more sliders. Johnson might have fallen into a pattern of overthrowing the fastball and speeding up his delivery. A few sliders would smooth his mechanics, and the next fastball would thump the strike zone.

There wasn't anything noticeably different about Strasburg's mechanics last season. He just appeared to be tinkering with a new strategy, trying to get quick outs with ground balls by taking a few miles off the fastball, instead of striking out 11 hitters per nine innings like he did two years ago and racking up a lot of pitches early in games. 

Like adopting the slider, that strategy was just one of the ways pitchers try to evolve. Justin Verlander used to throw every pitch as hard as he could as soon as the game started, but he didn't become the guy we know until he learned to pace himself early in games so that his 99-100 mph fastball was still there in the eighth inning. 

Strasburg's arsenal already includes three elite-level pitches, so if the slider just plays average or slightly better, that will be enough to take him from very good to one of the best in baseball. 

Strasburg is just 25 years old and very much in the prime of his career. Now with no restrictions on his arm, he's free to experiment with some things to let him reach the potential everyone saw on draft day five years ago. 

Note: All stats courtesy of Baseball Reference and FanGraphs unless otherwise noted. 

If you want to talk baseball, hit me up on Twitter. 


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