If Nick joined her team, even temporarily, she would NO QUESTION win every tournament she entered. With his brains and her power and experience, the FEAR would definately be back. Nick can scout better than anyone else in the biz, and Serena's got the killer instinct. She just needs to be healthy.
Career Grand Slam in your 20s? Been there done that. Career golden slam your 30s?
There's only 1. Serena.