Heartbreak for central defender after he suffers a knee ligament injury in England's first training session in Rustenburg

Fabio Capello was left to lament the "curse of the captain" tonight after Rio Ferdinand was ruled out of the World Cup with a knee ligament injury sustained in training. The Manchester United centre-half is braced for up to eight weeks in rehabilitation after twisting the joint as he stretched to tackle Emile Heskey in the last few minutes of England's morning session at the Royal Bafokeng sports campus today.

While the clash had appeared innocuous, Ferdinand's agonised scream immediately alerted those present to the gravity of the incident. The 31-year-old was helped from the training pitch in obvious discomfort and, along with the national team doctor Ian Beasley, was taken by ambulance to the Netcare Ferncrest hospital in nearby Rustenburg to undergo a scan.

Doctors later confirmed he had sustained damage to his medial ligaments and, while the Football Association did seek out a second opinion, it subsequently conceded the player had been ruled out of the tournament.

Initial estimates that the centre-half could be out for four to six weeks could yet prove optimistic, with the player himself fearing he will be absent for nearer two months, rendering him doubtful for the start of the new Premier League season.

Capello, frustrated if pragmatic as ever, has called up the uncapped Tottenham Hotspur centre-back Michael Dawson, 26, as an emergency replacement, with Steven Gerrard installed as England's captain for the finals and Frank Lampard stepping up to vice-captain.

"The other players were upset, absolutely," Capello said. "Training stopped and, although I hadn't seen the incident, Rio told me he'd put his feet down and twisted in the tackle with Heskey, then he felt big pain in the knee. Big pain. It's the curse of being the captain again and, it's true, it couldn't have been much worse on our first full day.

"All the players here with me are important, but Rio is one of the players who starts the games and is the captain, and a leader. It is obviously bad news and everyone with the squad is very disappointed and sorry for Rio. It was an accidental injury in training, and had nothing to do with the pitch."

Dawson, unused in the recent friendlies against Mexico and Japan and utterly untried at this level, flew out from Heathrow to Johannesburg tonight as a replacement after spending the day with his wife, Anna, celebrating their first wedding anniversary. He will now compete with Matthew Upson, who has started nine of the last 17 England matches, and the experienced if only recently recalled Jamie Carragher and Ledley King for a place alongside John Terry at the heart of the England defence.

"It's a crazy game and things can change in a split second," Dawson said. "One minute I'm trying to arrange my holiday, then I get a call asking if I was on holiday because Rio had pulled out of training. I said 'no' and then I was just waiting by the phone before getting a call saying I would be picked up in an hour. It's been a crazy day. For Rio to get injured, there would be no worse feeling for him as a player. To miss the biggest tournament in the world as the captain, I feel for him. I missed the Carling Cup Final in 2008, and there was nothing anyone could have said to me that could have made me feel any better. For Rio, the feeling will be the same, but it's a chance for me now.

"I've not had time to think about it but I've had call after call with people wishing me good luck. I know all the lads through having been with them for two weeks so I'll just be going out there and training as normal.

"I was planning to watch the first game of the tournament with my friends and family, but now I'm going to be there for real. I'll be going out there still having not yet won a senior cap, so where better place to get one if that was to happen. But I'll just go there and train like I do every day at Spurs and we'll have to see what happens. It's great to have four other Spurs lads out there as well."

While Capello's squad perhaps boasts more depth in quality at centre-half than in other areas of the team, they have achieved only seven clean sheets in 24 games under Capello to date and doubts remain over King's ability, in particular, to play twice in a short period of time given his own chronic knee complaints.

That will remain a concern for the England management staff, who had deliberately tested the 29-year-old Spurs captain to the limit during the recent training camp in Irdning, Austria, albeit under the supervision of the Spurs physio Nathan Gardiner. King played all of the 3-1 win against Mexico at Wembley, but was not involved in the friendly against Japan in Graz and trained alone with the physios today while the rest of the squad completed the session.

Yet, as Capello considers his options with the opening Group C fixture against the USA a week away, the squad's thoughts linger on Ferdinand. The injury represents a crippling blow for a player who had been selected for a fourth successive World Cup finals – he did not play at France 1998 – but whose domestic season had been wrecked by a succession of back and related groin problems.

The defender had started only 19 of United's 55 games in all competitions last term - he has missed 10 of Capello's 24 games in charge to date - and had displayed an understandable rustiness in the two recent friendly victories. Yet to suffer such a serious injury unrelated to those back problems in only England's second training session in South Africa was cruel, the defender returning from the hospital on crutches with a blue brace strapped around the joint.

The FA's medical staff were in regular contact with the United club doctor, Steve McNally, thereafter with the player expected to return home over the weekend. Capello himself was all phlegmatic acceptance, publicly at least, though this is the latest in a line of problems with which he has had to contend in recent months. The Italian has seen the chief executive, Ian Watmore, and the chairman, Lord Triesman, depart the FA; has lost David Beckham to an achilles injury and Wayne Bridge to premature international retirement; and felt compelled to strip John Terry of the captaincy over off the field issues.

"Rio was always an important player for us, even if we have played games without him," said Capello. "But I have big confidence in my players, in the defenders we have. All the players here are ready to play for me. They're at the same level.

"This is what happens sometimes. It is normal for a manager. Normal. You have to take into account that something like this could happen: whether it is in a game or in training. I remember it happening to me in the build-up to a final when we had to do without Dejan Savicevic [for Milan ahead of the 1995 European Cup final against Ajax]. You have to deal with it. We just have to pray: help us. No more injuries.