Williams, 33, is expected to return soon, a source told Andrew Greif of the Los Angeles Times.
"I think we all knew that we could start the league. The key is can we finish it? I think that will be the big thing," Rivers said Friday, according to ESPN's Ohm Youngmisuk. "I think what the league has learned - that teams have already known - that it is more than basketball that comes up.
"Guys have life going on. You know, whether it be a family problem, a kid problem, a wife problem, or anything, there's issues that come in these guys' life. We give guys days off all the time because of it, but no one really notices it.
"But now when you are in the bubble, when you leave, it really targets it. So I think, in a good way, the public actually sees that NBA players are actually human and do have regular life issues going on."
Any player who leaves the bubble must undergo a minimum four-day quarantine period upon returning, assuming that player tests negative for COVID-19 each of the seven days before he returns, according to ESPN's Tim Bontemps.
Individuals who don't undergo daily COVID-19 testing while outside the bubble must reportedly quarantine for 10 days before being granted entry.
Williams participated in Wednesday's scrimmage against the Orlando Magic, scoring a team-high 22 points in the Clippers' 99-90 victory.