Hunter Pence of the Houston Astros currently holds the longest hitting streak in Major League Baseball. He remains hot after a good start, and is finally living up to the promise of his rookie season of 2007. He greatly improved his ability to make solid contact with the change up compared to his three down years.
From 2008-2010, Pence hit the pitch for power, but made many outs doing so. His slash line of .249/.301/.464 on the pitch was good for a .327 wOBA. Pence made contact with the pitch, but failed to square it up:
In 2011, he makes solid contact:
With Hunter making better contact, his slash line on the change in 2011 stands at .360/.385/.600 a great .418 wOBA.
The whole point of the change up is to throw off a batter's timing. It looks like a fastball, so he swings early, and makes poor contact with the ball. Pence appears to have learned to recognize this pitch better, and his batting statistics improved with it.