Liverpool’s hopes of qualifying for the Champions League suffered another blow last night when Glen Johnson was ruled out for at least a month with a tear to the medial ligament in his right knee.

Johnson suffered the injury during the Barclays Premier League victory away to Aston Villa on Tuesday evening. There were initial fears that the England right back could miss the rest of the season and the World Cup finals in South Africa, but a scan yesterday revealed that the damage was not as bad as suspected.

The player will see a specialist today, when Liverpool say that they “should be able to more accurately determine the length of his rehabilitation period”.

If Johnson is out for longer than a month, he could miss the Merseyside derby against Everton at Anfield on February 6 and the Barclays Premier League match away to Arsenal four days later.

Although questions remain over his defensive ability, Johnson has been one of Liverpool’s main attacking outlets this season and his absence could not have been more poorly timed after Rafael Benítez’s team moved to within four points of fourth place with their win at Villa.

It remains to be seen if Johnson’s injury will force Benítez into the transfer market for a right back, although with any money he can raise from player sales earmarked for a new striker, the manager may have to get by with what he has in reserve.

While Liverpool will feel that they have boosted their chances of claiming a top-four spot considerably by beating Villa, recent history suggests that they will still miss out, and that the battle for fourth place is between Tottenham Hotspur, Manchester City and Villa.

The bad news for Liverpool, who will see out 2009 in seventh place, is that no team outside the top six on New Year’s Eve have made it into the top four on the final day since the 2000-01 season. On that occasion, Leeds United made an impressive jump from fourteenth to fourth, winning 13 of their final 19 league matches and also reaching the semi-finals of the Champions League.

Since then, the team who have finished fourth have either been in the same league position on December 31 the previous year or no lower than sixth. Of the contending teams, Spurs, who are fourth, should be looking ahead with most optimism. In six of the past eight seasons the team who began the year in fourth place have either stayed there or improved their final position.

However, Jamie Carragher was not letting the facts get in the way of a good story after Liverpool’s victory, secured with an injury-time goal by Fernando Torres after some bizarre defending by Villa. “It is a big result,” Carragher said. “Obviously 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.

“Over the last few years, Villa have been one of those teams around the top six alongside Everton. But Manchester City have come on and Tottenham have done really well, and I think they are all looking at us as the team whose place they can take.”

Villa were fourth before successive defeats by Arsenal and Liverpool. However, Luke Young believes the increased competition for Champions League places can lessen their pain.

“Teams are taking points off each other left, right and centre,” Young said. “It’s going to go down to the end for this final Champions League spot and we hope to be in among them.”