The gun centre, who has already missed plenty of time this season with a sickening elbow injury, had only returned to action during Round 17 in a loss against the South Sydney Rabbitohs.
The contest saw him score a try and run for 79 metres.
The Knights have now revealed that a thumb injury is behind him not being in this week's team however, with the star centre going in for surgery which is set to rule him out for anywhere between three and four weeks.
"Bradman injured his thumb in the last round," Newcastle head of medical Craig Catterick told club media.
"It's the other thumb, not the one that he had well documented in the pre-season.
"He has pulled the ligament and a little bit of bone off, so he is having surgery today to have that reattached and should hopefully be back on the field in about three to four weeks."
Catterick also confirmed that both of Newcastle's Origin players - Kalyn Ponga and Jacob Saifiti - have recovered well from Origin and will take their places against the Manly Sea Eagles on Saturday evening.
Best has been replaced in the team by Enari Tuala for the clash against Manly, after Tuala had made way for Best's return last week. That followed the recent form of Edrick Lee and Dominic Young, making the wing duo virtually undroppable.