Based on how the announcers are describing Durant's injury, it sounds more like a Grade II Calf Strain than a Grade I. If that were the case, then even if the Warriors make it back to the Finals, K.D. wouldn't be back until mid way through the Finals.
Pancho A. Ovies
Nintendo Switch in Japan (Famitsu): 2018 vs. 2019
PlayStation 4/Xbox One/Nintendo Switch: 2018 vs. 2019