In early August of last season, Yankees' center fielder Curtis Granderson went to hitting coach Kevin Long for help with his swing. From that point on, Granderson was performing much better at the plate. It could just be a combination of small sample size and selective endpoints. You can judge for yourself.
I also noticed that Granderson was producing better results on pitches up in the zone. If we isolate pitches thrown to the top 5 inches of the average strike zone and higher, Granderson's slugging percentage went from .403 to .816. His swing rate, as well as miss rate, didn't really change at all. We're only dealing with 365 and 288 pitches in this specific zone over the two time periods respectively, however, so you can't read too much into his results. Although I will say that a change in his expected OBP might indicate a better approach. Before August 10th, Granderson had an exp-OBP of .363 with a 17.2% exp-BB% on pitches up. From the 10th on: .421 exp-OBP, 20.8% exp-BB%.