Williams is expected to return to rugby league with the Sydney Roosters in the 2013 NRL season.
A part-time boxer, he is the New Zealand heavyweight champion and is scheduled to take on veteran Botha, 44, a four-time world title challenger, in Brisbane on November 24 in his sixth pro bout.
Williams, who is on a contract to play 12 matches for Panasonic reportedly for $1.2 million, scored a first-minute try, his second since joining the team, in the Top League eighth round.
But he crunched his shoulder attempting a tackle on former Western Force centre Gene Fairbanks 10 minutes into the match.
He left the field and Panasonic went on to beat Kintetsu 23-20 for their fifth win against three losses.
Panasonic stood fifth in the league table while defending champions Suntory Sungoliath are top.
The Top League has now gone into a five-week break with its final set for late January.
-AAP