I recently bought Rocket League and whenever I play online my performance drops under 40 fps averaging around 25 fps. I don't experience any performance drops or lag when I play offline in training or free play. I have a 1080 SC and a i7 6800k @ 3.4ghz.
PC Specs
EVGA GTX 1080 SC
I7-6800K @ 3.4ghz
16Gb Corsair Vengeance 2133MHz
PC Specs
EVGA GTX 1080 SC
I7-6800K @ 3.4ghz
16Gb Corsair Vengeance 2133MHz