With Halfpenny definitely out, Wales will have to decide who to bring into their 31-man squad, with Anscombe, James Hook, Eli Walker, Rhys Patchell and Tyler Morgan all options.
Coach Warren Gatland could choose instead to introduce another wing such as Eli Walker or go to a 18-13 forward-backs split and pick a third hooker.
Local media think Anscombe is the favourite if fit, given he's a reliable goalkicker and is experienced playing at fullback. Reports suggest Wales might delay a decision on Halfpenny's replacement while they monitor Anscombe's fitness.
Anscombe made his debut for Wales against Ireland on August 8 and was expected to make the 31-man squad for the World Cup until his training mishap.
Wales' hopes of progressing from a World Cup group that also includes England, Australia and Fiji (and Uruguay) took a dive with the injuries to Halfpenny and Webb and it didn't take long for the finger-pointing to start.
Shane Williams and JJ Williams questioned what Halfpenny was doing on the Millennium Stadium pitch in the final warm-up against Italy.
"To lose Halfpenny, who has been the form player over the last four to five seasons, the player to get us out of trouble, is just a massive kick in the teeth and Wales is in mourning," Shane Williams said at ITV's World Cup launch.
"I saw Leigh warming up and -noticed his knee had been strapped up and, you thought, 'Do we need this guy on the field? Let's wrap him up in cotton wool and roll him out when we really need him'. To me, it just looked that he wasn't fit anyway. He wasn't the same under the high balls as we've seen over the years and looked a little bit -uncomfortable.
"You have players like Matthew Morgan included in the squad, and a lot was mentioned about him getting a run at full-back. And, of course, you have Liam Williams who is just coming back from injury and isn't quite there. So you could see why they had to go with Halfpenny or Morgan, but Leigh's such an important player, maybe he didn't need the game-time as much as Morgan or even Hallam Amos maybe."
Williams's namesake was similarly bemused at the selection of the man of the series on the last Lions tour.
"The bandaging on his leg was quite enormous, wasn't it? So there's a problem there," Williams told BBC Wales. "It was a bad decision to play him. It was the ideal chance to give Morgan a run-out at fullback. They are paying the penalty. Now we've got a deep problem of who is going to replace him."
Gatland has been around long enough and, more pertinently, in Wales long enough, to shrug off these comments, but there is no doubting the mess it has made of his plans.
Former England hooker Brian Moore wrote in The Daily Telegraph that the absence of Webb and Halfpenny could prove "fatal to Wales' challenge".
- Additional reporting UK Telegraph
