The England right-back was assessed by the club's medical team at Melwood earlier today and underwent a scan which revealed the extent of the injury which forced him to limp off after 88 minutes of the 1-0 victory at Villa Park.

A club spokesman said: "A scan today has revealed a tear in the medial ligament in Glen's right knee.

"The player will see a specialist tomorrow, after which we should be able to more accurately determine the length of his rehabilitation period."

Fans of both Liverpool and England will be hoping Johnson is not facing a long spell on the sidelines.

The 25-year-old left Villa Park on crutches last night - as a precaution - and has already missed three games this season with calf and groin problems.

It is the latest setback in a season that has seen influential pair Steven Gerrard and Fernando Torres struggle to overcome injuries, while £20million midfielder Alberto Aquilani's debut was delayed by ankle trouble.

However, Jamie Carragher believes Liverpool's victory last night was a statement of intent to their rivals that they are still a major force in the battle for a Champions League spot.

The Reds closed the gap on fourth-placed Tottenham to four points, and are now only two behind Villa, after Fernando Torres scored his 50th Premier League goal for the club in the third minute of injury-time.

Liverpool boss Rafael Benitez reiterated his "guarantee" of finishing in the top four in the aftermath of the Villa Park encounter.

And Carragher is confident they can now put together a decisive run of results in the New Year.

He said: "It was a big result. That brings us a lot closer to Aston Villa. If they had beaten us, it would have been a big points difference so the one game can make a difference.

"We realise what would have happened if we had lost. People would have said we were miles away and that was it for the top four so we have given ourselves a fighting chance.

"I haven't looked at the table for a while so I am not sure how far or how close we are. When it's not going well, there is no point.

"But, if we can win the next game against Tottenham as well, that can put us right in the mix. We've had a lot of ups and downs this season and hopefully we can go on a good run now."

Carragher added: "We've been up there for a long time. There are always people wanting to shoot you down, other teams.

"Over the last few years Villa have been one of those teams around the top six alongside Everton.

"But this time around Manchester City have really come on and Tottenham have done really well and I think they are all looking at us as the team they can take the place of.

"So it was more than just the three points at Villa. It was a statement to everyone that we are still fighting for that place."

Villa were left to reflect on a dismal festive period that also saw them beaten by another of their top-four rivals in Arsenal.

But defender Luke Young is confident Villa will not suffer a long-term hangover from their double setback ahead of FA Cup third round and Carling Cup semi-final meetings with Blackburn in the next week.

He said: "Everyone was disappointed in the dressing room but we can't let the last two results ruin the great run we've had.

"It's time to regroup now and look forward to the tough month we've got coming up. Let's get over this one and look forward to the weekend.

"We've got to look forward. If you start dwelling on results like the Liverpool one, it's the worst thing you can do. You can start beating yourself up.

"We've seen in the league this season that teams are taking points off each other left, right and centre.

"It's going to go all the way down to the end for this final Champions League spot and we hope to be right in among them. We want this to make us stronger."

Villa will be hoping striker Emile Heskey has recovered from illness in time for the first meeting with Sam Allardyce's side on Saturday.

Villa boss Martin O'Neill said: "Emile was ill on Sunday at Arsenal and he came off in the game and still wasn't feeling so bright so we didn't include him. We will see how he is."