Seasons change. So do surfaces. Will clay slow down the tour's hottest hitters? The Insider Team fires up the Heat Index to discuss the 12 hottest players heading into the spring clay season. Karolina Pliskova, Serena Williams, Johanna Konta, Caroline Wozniacki, and Venus Williams dominated the hard courts, but can they sustain their momentum as the tour hits the clay? Courtney Nguyen and David Kane discuss.