England fear Alex Corbisiero will miss the entire spring The red-rose hierarchy are doing their best to put a brave face on it, but the immediate future of England's senior loose-head prop Alex Corbisiero is clearly causing Stuart Lancaster and company serious concern. The London Irish forward's chronic knee problems require a second bout of surgical intervention and while the imminent operation is considered to be relatively minor, its potential implications are significant. One of the key figures in Lancaster's rejuvenated pack - the head coach regards him as one of his "go-to men" when the stakes are at their highest - Corbisiero will definitely miss the opening Six Nations games with Scotland and Ireland. There is no guarantee he will feature at any stage of the tournament, even though the player himself has dismissed talk of a "degenerative knee condition" and expects to be playing club rugby early next month. "His knee keeps swelling up after small amounts of exercise," Lancaster reported. There's a loose body in there somewhere and it needs cleaning out. His knee locked up when we were in South Africa last summer and since then we've struggled to get him training and playing consistently. A lot depends on this next procedure, but we're optimistic. At 24, Corbisiero is still in the foothills of his front-row career, and some of those working with him believe he would benefit by switching to the tight-head side of the scrum, thereby easing the pressure on his troublesome knee. As things stand, England are not the only ones worrying about his prospects. Northampton, who have signed him for next season at considerable expense, are also wondering what the next few weeks might hold. England may also start the Six Nations without the free-scoring Leicester centre Manu Tuilagi, whose "human bowling-ball" style has been a feature of the national side's attacking game in recent matches. Tuilagi is suffering from ankle trouble and will have to prove his fitness by the weekend if he is to play a part against the Scots. According to his club, he was 20 minutes away from facing Toulouse in last Sunday's big Heineken Cup match at Welford Road. As far as England are concerned, he is many hours away from being able to train properly, let alone play. If he withdraws, Lancaster could simply replace him with the London Irish centre Jonathan Joseph or re-jig his entire midfield by restoring Toby Flood of Leicester to the outside-half position and moving Owen Farrell of Saracens further out. Alex Goode, the first-choice full-back, has recovered from a shoulder injury and is expected to shake off the after-effects by turning out for Saracens this weekend. The news on Tom Johnson is far worse. The Exeter flanker suffered a nasty knee injury last weekend and is likely to be incapacitated for at least three months. As for the Gloucester outside-half Freddie Burns, the exciting newcomer to the Test squad will spend the next three weeks on the casualty list after damaging knee ligaments last week.