before you put it completely on Williams, you have to see first what Carlesimo was trying to run. if he gave the reigns to Williams, then there's a point to an extent.
it's not like Williams was going 1 on 1 the whole night. even on the corner miss by Joe Johnson, he was being hounded by 2 guys off the pick and roll and Brooke Lopez wouldn't take the shot twice.
you can't do much if you're being doubled and your big man doesn't want to do anything. Williams did make some big plays to bring them back. don't know what else you'd want from the guy (a PG) being doubled by his man and another bigger guy.