The great experiment is over: Stephen Strasburg is no longer throwing the slider.
The last time he threw the slider with any regularity was in mid-April, when he was rocked by the Marlins for six earned runs in four innings.
It was not an effective pitch for him at all. According to BrooksBaseball, Strasburg threw the slider 47 times this season – almost exclusively to right-handed batters (46 of the 47 pitches). In 11 at-bats, hitters produced four singles and a home run while striking out five times. Small-sample-caveats apply, but his slider was hit for home runs twice as often as his fastball this season.
For a pitcher like Strasburg who can bring the heat and has a phenomenal change-up, it’s best to go with what works.