Wales hold their breath over star duo
Gatland watched in horror as two of his key players were carried off on stretchers in an unconvincing 23-19 win over Italy in Cardiff on Saturday.
Webb suffered suspected serious ligament damage to his ankle in the first half after falling awkwardly at a ruck. And Halfpenny's right knee, already heavily strapped, then gave way as he moved to collect a kick 11 minutes from time.
Gatland and Wales now face an anxious wait on the result of scans, having already lost centre Jonathan Davies earlier in the year, before considering any replacements.
Gatland said: "It's not great. You have got to feel for them if they are ruled out of the World Cup. It would be a massive blow for them and disappointing for us.
"It's just one of those things in rugby. Players want to play but unfortunately they can pick up injuries. Look at the second Test in South Africa last summer (when Wales came within seconds of beating the Springboks), neither of those players were involved.
"So if they are ruled out we will have to put that behind us, work with the players we've got and build towards the next game.
"Liam Williams has taken a full part in training and potentially over the next 48 hours, when we get the results of the scans, we may have to sit down and look at picking replacements."
Williams is a ready-made replacement for Halfpenny after recovering from a foot problem. Gareth Anscombe, nursing an Achilles problem, or James Hook could also be considered for call-ups.
Mike Phillips is the natural choice to replace Webb, particularly given the lack of experience between remaining scrumhalves Gareth Davies and Lloyd Williams.
Captain Sam Warburton revealed the squad had been left shaken by the potential loss of two key players.
He said: "It would be gutting if they are ruled out after putting in so much effort. There's no getting away from the fact they are two huge players for us.
"I'm going to be optimistic and hope that if it's just a grade one or two tear to the ligaments that is something you can come back from in three weeks, even though they feel worse at the time.
"You do really worry for them when you see guys who are your mates go down in real pain. It hits the rest of the players as well.
"I really hope they are ok. We're all keeping our fingers crossed for the results of the scans on Monday."
Italy also suffered a double injury blow of their own to centres Luca Morisi and Gonzalo Garcia.
Morisi is out of the World Cup after tearing knee ligaments, while Garcia is also a serious doubt with ankle damage.
Captain Sergio Parisse said: "It's terrible for anyone to be injured at this stage, so close to the World Cup. We lost a young player last week (Angelo Esposito) and we have two more worries now. But this is rugby and can give strength to the rest of the team."
AFP
