Obviously we don't know the details but if it was small he probably had laparoscopic surgery and recovery time might not be too long. Sounds like there was no evidence of spread so he won't be on chemo or anything, just has to heal from the surgery (and the stress of everything). He's not going to be back in a week or anything but I would think he should be back this season if he doesn't have any setbacks.
Honestly he's just super lucky he got traded at the right time. I assume it was discovered incidentally, probably on a lumbar spine MRI. This is always one of the big concerns radiologists are worried about missing at the edge of the field of view on lumbar spine MRI's, as catching renal cell early has good prognosis but once it has spread the prognosis is not good.
Either that or he got a routine urine sample that had blood in it, and then he got some dedicated renal imaging for that reason.
Regardless, very fortunate for LaVert. The reports say "small", and under 3-4 cm they are unlikely to have already spread.