The injury is similar to the one which cut short Craig White's trip last month and is expected to take between four and six weeks to heal. Martin McCague (shin stress fracture) was the first to head home, followed by White and then Darren Gough (stress fracture of the foot).
"It has been an unbelievable tour for injuries," the England physiotherapist, Dave Roberts, said. "I've never known anything like it. Thirteen players have been unavailable for matches at various times and people want to know why there have been so many problems.
"I don't think there is a simple answer but I plan to compile a full report for the Test and County Cricket Board at the end of the tour. Hopefully, I will be able to come up with some constructive suggestions. I won't be looking for excuses, just reasons."
But there is little prospect of the heavy workload for England's players getting any lighter. After the West Indies tour this summer there will be no more than three weeks' rest before embarking on a five-Test tour of South Africa, which also includes seven one-day internationals, followed by the World Cup in India, Pakistan and Sri Lanka.
Udal had to admit defeat after visiting a Melbourne specialist. He has been fighting the injury for more than a week and needed pain-killers to get through two World Series Cup games.
"It's disappointing for my tour to end this way but I've no regrets about having played on," he said. "It wasn't a gamble in my eyes because I knew that whatever happened I would have three months to get fit for the new season."
Udal, having missed out on selection for the first three Tests, was not expected to figure in the final two matches of the series and will not be replaced. One piece of good news for England yesterday was the return of the vice-captain, Alec Stewart. Stewart, who broke his right index finger on Boxing Day during the second Test against Australia in Melbourne, played for a David Gower XI in the Origin of the Ashes match at Sunbury, making 48 in only 35 balls.
"It felt all right, there were no problems at all," he said. "It's still not 100 per cent, but I hope to play against Victoria in Bendigo."
Mike Gatting and the wicketkeeper Jack Russell also played in the match, which the England XI won by one run against an Australian selection.
Waqar Younis and Allan Donald, two of the world's outstanding fast bowlers, may miss the inaugural Test between Pakistan and South Africa starting in Johannesburg today.
Waqar aggravated a hamstring strain in the second Mandela Trophy final against South Africa last Thursday and did not practise with the team on Tuesday. Pakistan's manager, Intikhab Alam, said: "Waqar is very doubtful for the Test and I don't think he'llplay."
The pace bowler Aamir Nazir has been flown from Pakistan as cover but, if Waqar is ruled out, his place is likely to go to either the uncapped left-armer Kabir Khan or the seamer Ata-ur-Rehman.
Donald was included in South Africa's squad of 13 for the one-off Test at the Wanderers but is not certain to play. He missed the recent series against New Zealand because he was recovering from a cyst on his right big toe suffered on last year's tour ofEngland.
The South African coach, Bob Woolmer, said: "Allan Donald will have to prove himself fully fit before he gets back his place in the Test side. He hasn't played since August apart from two one-day matches so he's not match-fit. If we play him it will be agamble."Reuse content