I have had this happen in two different leagues of mine in the past and each was handled differently-
1. The league voted on a projections website that would be used to set the guys lineup and each week the commish was responsible for getting the lineup set. This was not only a pain in the arse for the commish, but it also presented a problem because the phantom team started winning some games and would have made the playoffs. The team who finished right behind in the standings took the playoff spot, but it was odd.
2. We did what awwchrist suggested and used the average which worked out much better.
Best-case-scenario is to find someone to take over his team, but if you can't do that then use the average.
Are you looking for someone to replace him? How much was the league?
"I'm normally not a praying man, but if you're up there, please save me Superman."
- Homer J. Simpson