I believe the heat expected to reach mid 90's by match time will help Tsonga's serve. I've also noticed that the daytime matches have ended more in 3 setters vs the night time at Indian Wells the past few days. Even though Djoker's been playing lights out so far, if Tsonga has a boost on his serve, that Over 21 number will cash today.
Best of luck
-----------------------------------TSONGA/DJOKOVIC OVER 21 -------------------------------