Left-handed batters performed poorly against Giants closer Brian Wilson in 2010. They batted .206 against Brian, compared to .232 for RHB. Wilson did a great job of keeping pitches away from lefties:
On strikeouts, he comes no where near the center of the zone.
He's either getting good calls from the umpires, or Wilson is very good at fooling lefties at swing at pitches out of the zone. It tuns out it a bit of both, and umpires give him lots of leeway on the low outside corner.