But, technically even based off an April 30th article on here, he wouldn't need to "learn" anything, just bring back the slider he had. Fastball, sweeper, slider, curve may help. I think it was the Rockies game... It was basically fastball, curve, fastball, curve or fastball, sweeper, fastball sweeper.
I'm not saying 2 or 11 is a lot but I figure occasionally throwing it could help if you know you're getting either 94 or 74mph every pitch