From the NYT
John Isner, who at No. 14 is the top-ranked American in the A.T.P. rankings, has parted ways which Craig Boynton, who had served as his coach since March 2009.
Isner has hired Michael Sell as his coach for 2013.
After serving as the personal coach of Monica Seles, Sell began to work with the United States Tennis Association in 2003, eventually rising to the level of lead national coach for men’s tennis. He has at various times worked more closely with Isner, Mardy Fish, and Donald Young.
A good move. I think his relationship with Boykin ran its course. I hope Sell-Isner partnership will be successful.