How Chris Archer's Slider Made Him an Elite Pitcher

In April, numberFire’s John Stolnis called Tampa Bay’s Chris Archer the best pitcher in the American League East.

In the month and a half that has followed, not only has Archer proved John right, but the Rays righty has put himself in the discussion for best pitcher in all of baseball this season.

In 83 innings, the 26-year-old has a 1.84 ERA and 51 ERA-, ranking fourth and fifth best in the Majors, respectively, among qualified starters. This has not been some ball in play fluke either, as Archer’s 33.3% strikeout rate leads all qualified starters, as does his 27.2% K-BB%, FIP- (53), xFIP- (55), cFIP (62) and SIERA (2.30).

Archer came into the season with a 92 ERA- and 12.7% K-BB% in 352.2 big league innings, so while he had been an above-average pitcher to start his career, his start to the season marks a huge step forward.

So what is driving this improvement?

A sizable increase in swinging strikes seems to be a prime cause, which itself has been driven by an increase in slider usage.

Archer came into this season with a swinging strike rate (swinging strikes per total strikes) of 15.8% but has upped this to 22.2% in 2015 to rank seventh among all pitchers in the Majors. He also ranks seventh among 183 starters who have thrown at least 200 pitches in whiffs per swing rate (31.12%), according to Baseball Prospectus.

Per Brooks Baseball, Archer’s slider has always been his best pitch in terms of generating whiffs, so it makes sense that throwing the pitch more frequently has led to more swings and misses.

He threw the pitch 27.96% of the time in his debut season in 2012, before throwing it 32.99% and 28.91% of the time in 2013 and 2014, respectively.

In 2015, he has thrown his slider 38.68% of the time, generating a 43.75% whiff per swing rate.

Archer is also throwing his fourseam fastball much more often relative to last season, using the pitch 46.20% of the time in 2015, up from 24.79%. The pitch, which Brooks Baseball has clocked at 96.2 miles per hour, has produced a 21.86% whiff rate this year.

The uptick in fourseam and slider usage has coincided with fewer sinkers and two-seam fastballs, a pitch he has only thrown 7.44% of the time in 2015. That pitch led to a whiff rate of 13.97% last season and 13.16% this season.

The tweaked pitch usage helps explain how Archer’s strikeout rate this season marks a 12.2% increase from his previous career average.

Strikeouts have only been part of the equation, though, as Archer is also walking fewer batters, issuing a free pass to 6.2% of the hitters he has faced this season. Prior to the start of this season, Archer’s walk rate was 8.4%.

This improvement has coincided with Archer posting a career-high first strike percentage of 62.8%, a 4.8% increase from his previous career mark.

As for the third of the “three true outcomes,” home run rate, Archer ranks in the top 20 at 1.6%, despite a home run per fly ball rate of 9.4% that is around the league average. An above average groundball rate of 49.0% explains this disparity, and for this, he can again thank his slider.

Since 2013, Archer’s slider has produced a grounder rate above 50.0% with that number spiking to 54.05% this season, according to Brooks Baseball.

The combination of these factors has helped turn the best pitcher in his division into one of the best pitchers in the game.