It is never hard to understand why England persevere with Stuart Broad. Even on days when his body seems fragile, when he looks more of a slogger than the classy batsman he has shown he can be and when he releases the ball with all the force of a shuttlecock, he still looks as if he has all the raw ingredients to develop into a top-class international cricketer.

Perhaps he already has. After all, aged 27, he has passed 200 Test wickets, scored nearly 2000 Test runs and played a part in a World Twenty20 win, three successful Ashes series and the England team achieving the No. 1 Test ranking.

Yet the sense is there is more to come. The sense is that, with all that ability and all the faith the England selectors have invested in Broad, that he should be even better. That good isn't good enough; he has to be great.

That is quite a burden for a young cricketer. But when Broad first appeared in county cricket, he looked a player of such outrageous potential that there were hopes he could develop into something approach Glenn McGrath as a bowler and Andrew Flintoff as a batsman. That is a desperately high bench mark.

That may be part of the reason some have become infuriated with him. He has so much natural talent and so many of the advantages that were denied his predecessors - not least a central contract and the security of continuity of selection - that a Test bowling average of 31 and a batting average of 25 appear a disappointing return six years into a Test career that promised more.

It is true that Broad has, at times, been more decorative than functional. Times when he has been long on potential and short on delivery. When watching him has been like waiting for a Faberge egg to hatch.

But whenever you think you can write off Broad, he produces a performance like this. A performance of such undeniable class and skill that it would seem madness to even contemplate dropping him. When, after all the time invested in him, it still seems he might just fulfil all those lofty ambitions people had for him.

He does not do it often enough, of course, but even this year - a year when he has supposedly struggled - he has taken two five-wicket hauls against New Zealand and is on the brink of another against Australia. His figures in this series did not flatter him, either. He bowled well at Lord's and Old Trafford without a hint of fortune.

Broad was comfortably the best of England's bowlers on the second day in Durham. Partly as a result of his height, but mostly as a result of his skill, he generated more movement than his colleagues and maintained an immaculate line and length just on or outside off stump.

David Warner was undone by a beauty that seamed in, Usman Khawaja by one that had him unsure whether to play or leave and Chris Rogers was beaten more often than a snare drum as Broad, swinging the ball away but seaming it in, plugged away on off stump. Rogers later praised it as "an unbelievable, beautiful" spell of bowling. Broad finished the day with four wickets, but could have had several more.

At present, he requires a bit of assistance from conditions to be truly effective. It is not so much that he does not have the skills to contribute on the flattest of pitches - he did so in the UAE and Sri Lanka, after all - it is more that he does not always seem to have the heart for it.

In India, for example, there was a perception - possibly an incorrect one - that he did not have the stomach for the tough job required of him on flat surfaces and as one of only two seamers. Instead of rolling up his sleeves and embracing the glamour-free task - and the no-excuses culture - Broad spoke of illness and injury and finally went home early. The impression given at the time was that the England management were underwhelemed.

Perhaps that was harsh, though. Perhaps the foot injury and food poisoning that Broad sustained really did contribute to his lacklustre performance and Broad's real problems, once again, were the unrealistic aspirations we have had for him.

He has already had, by most standards, a good career. And, if he can remain fit and perhaps invest in a little more time in the gym to ensure he has the strength required for the rigours of his role, there is no reason the best should not be ahead of him.

Broad's performance came in stark contrast to that of James Anderson. On the sort of pitch that Anderson must dream about, he appeared, for the second Test in succession, jaded and lacklustre. He did not bowl badly - he almost never does - but by the standards he has set, it was an oddly neutral performance.

It may be facile, but it is worth reflecting for a moment on what the reaction might have been had Graham Onions played ahead of Anderson in this Test and produced an identical performance. He may well have been jettisoned forever. Anderson will certainly - and correctly - not suffer such a fate, but all the signs indicate he requires a break. A strong case could be made to suggest he has played his last international cricket of the summer.