Liverpool will be without the services of Daniel Agger and Xabi Alonso for up to six weeks after it emerged last night that both players had fallen victim to a fractured metatarsal, the injury that is the curse of modern-day football.

Agger, the Denmark defender, and Alonso, the Spain midfield player, missed Liverpool’s unconvincing 1-1 draw away to FC Porto in the Champions League on Tuesday and were sent for X-rays on their return to Merseyside yesterday afternoon. Agger’s fracture is in his right foot, Alonso’s is in his left.

It is a double blow to Rafael Benítez, the Liverpool manager, with the two players in danger of missing up to six Barclays Premier League matches, including fixtures against Tottenham Hotspur, Everton and Arsenal in a three-week spell next month, as well as Champions League matches against Marseilles and Besiktas.

Alonso suffered his injury during a training session in the Estádio do Dragão in Oporto on Monday evening. Agger, having bruised his foot in the goalless draw against Portsmouth on Saturday, is understood to have aggravated his problem in the same session.

If any squad should have the strength to cope with such setbacks, it is Liverpool’s, particularly in midfield, where Benítez has Lucas Leiva, the young Brazilian, to bring into his plans, as well as Steven Gerrard, Javier Mascherano and Mohamed Sissoko.

But the picture is less rosy in central defence, where Agger’s injury leaves Jamie Carragher and Sami Hyypia as the club’s only fit senior centre halves. Benítez may be forced to call up one of last season’s FA Youth Cup-winning squad, such as Jack Hobbs, the reserve-team captain, who is likely to make his first-team debut in the Carling Cup third-round tie away to Reading next week.

Then there is the problem caused by Jermaine Pennant’s red card against Porto, with the winger suspended for the next Champions League match, at home to Marseilles on October 3. Benítez did not censure Pennant publicly, but he is known to have been dismayed by the player’s recklessness in diving into a late challenge on Fucile, the Porto defender, having been booked for a similar foul on Ricardo Quaresma in the first half.

Pennant suggested that he had been hard done by, a verdict that was not shared by his manager or his team-mates. He pointed out that most players are sent off at some point in their careers, “so please give me a little bit of leeway”.

It was not a performance that was likely to do him many favours in the eyes of Benítez or, indeed, Steve McClaren, the England head coach, who regards David Beckham, Shaun Wright-Phillips, Aaron Lennon and David Bentley as stronger candidates to play on the right wing.