Jonny Venters has thrown 191 sliders this season, and opposing hitters have swung at 103 of those sliders. Yet, of those 103 swings, they have hit nothing but air 70.9% of the time. That leads all major league pitchers throwing sliders. Sergei Santos of the Chicago White Sox comes in second with 64.9%, and there are only five other pitchers who have produced a Miss% rate on sliders greater than 50% this season.
You can see that he keeps the slider away from lefties, missing the strike zone the majority of the time, while keeping it on the bottom of the zone to righties. Venters has gotten opposing hitters to swing at his sliders located out of the zone 51.5% of the time. In fact, Lefties have chased 61% of sliders he's thrown out of the zone, which ranks 3rd best in the league behind Jaime Garcia and Joel Hanrahan.
Last season, Venters was getting hitters to swing and miss at 63.7% of his sliders and chase 41.5%. While both are still excellent overall (his Miss% also led the league in 2010), his current slider has gone above and beyond. Lefties are hitting just .115 against, while righties have yet to get a hit in 35 plate appearances decided on a slider. In fact, in the 61 PA in which a Jonny Venters slider was the deciding pitch, 51 have been strike outs (47 swinging, 4 looking). The fact that he can throw his slider effectively to both righties and lefties is a major reason he hasn't allowed an earned run since June 29th.