The season prior, Wilt Chamberlain was dealt to the Lakers.
Chet Walker, an all-star forward, was traded to the Chicago Bulls for Jim Washington, who played college ball in Philadelphia, and ended up having a journeyman career.
Luke Jackson continued to be hobbled by a major injury sustained in the previous season & never played the same again.
That, combined with a very poor draft, were factors in the team losing 13 more games than the previous campaign.
[1] This table only displays picks through the second round.