With England at the moment, you do not know whether to laugh or cry. Weep for the injuries that have reduced so many players to also-rans, among them the friendly fire that cost the services in the front row of David Barnes, or smile at the optimism that necessarily emanates from the camp but for which there seemed, at the last time of asking, little obvious justification.

The four changes from the starting XV that played Australia last weekend to the one that will meet Argentina at Twickenham on Saturday, the second match in the Investec Challenge Series, were entirely predictable. But they also affect three fifths of the side’s spine. That they involve the hooker, No 8 and scrum half suggests that some misjudgments may have been made before the 18-9 defeat by the Wallabies.

Considering the injury crisis that surrounds England, perhaps errors of judgment can be forgiven. Martin Johnson has never used the crisis as an excuse — the team manager acknowledges that you could argue as much for the retention, say, of Steve Thompson as against the promotion of Dylan Hartley — but these are the decisions that he believes to be right. In the harsh sporting environment in which he exists, Johnson knows that the only validation is victory.

Only one of the changes is enforced, that of tight-head prop, where David Wilson, suffering from a shoulder/neck injury, is replaced by Duncan Bell, his Bath colleague. En route to selection, Bell revealed that he was the man responsible for Barnes, another Bath player, joining the ever- lengthening list of injured props, just when he was on the verge of winning a first cap.

“I feel bad for David, who left on crutches [on Tuesday], and I was the one who did it,” Bell said. “I went to clean out a ruck, slipped and fell over the back of the ruck. David was on all fours there and I landed on the back of his leg, I heard a yelp and he was down for about five minutes.”

As Bell weighs in at 19st 8lb, Barnes’s grief was understandable and it may be that he will never come as close to a cap again. A fourth Bath prop, David Flatman, was called up for training but has now returned to his club, while Barnes’s misfortune has carried Paul Doran-Jones all the way to the England bench within the space of three days.

No wonder Doran-Jones, 24, exuded enthusiasm despite receiving a knock in training. Because he covers both sides of the scrum, he is virtually certain to win his first cap after a mere 266 minutes of Guinness Premiership rugby in his career.

“I’m trying not to overthink it, I don’t want to drown in the detail, I want to get out and enjoy the whole experience,” the former Wellington College pupil said.

The good thing for Doran-Jones is that he has some life experience to call upon, too: he took an upper second degree in medical chemistry from Trinity, Dublin, where he was also contracted by Leinster.

He has served his time in National Division One, with London Welsh (who trained with England this week), where he learnt elements of his job at the coalface. In his brief career with Gloucester, he has already played against Fabien Barcella, who props for France against South Africa tomorrow, and went well against Australia during this month’s game at Kingsholm. “It’s given me a better handle on things,” Doran-Jones said, and now he has the chance to prove it.

He will play alongside Hartley, whose elevation owes something to the strained hamstring that probably cost him a starting place against Australia. Thompson is on the bench, excited just to be a senior figure in an international squad that, not so long ago, looked beyond him.

He will be a mentor to his fellow forwards, among them James Haskell, who will form a new axis at No 8 with Paul Hodgson at his heels, at scrum half.

Haskell has played little or no rugby at No 8 for Stade Français this season so this will ask questions of his ability to control, as well as rampaging around the field, ball in hand. For a player who seemed to be dwindling to the sidelines this year, this is a huge chance to re-establish himself as the international force he looked to be two years ago and that he has always, in his public utterances, believed himself to be.

Hodgson’s appearance for his first start has considerable significance. Hitherto he has been regarded as back-up to Harry Ellis or Danny Care, but he has worked hard to carry his club form forward to the international arena where, remarkably, he will face a London Irish team-mate, Alfredo Lalanne. Moreover, the plaudits coming his way for his contribution in training suggest that, once he establishes himself, he will not be easily dislodged.

“Paul’s very good at ‘tempo-ing’ a game,” Johnson said. “I don’t think Danny played badly against Australia but Paul’s a bit more experienced. He brings a bit more leadership with him and what he brings around the group is real maturity.”

Given the exigencies of England’s situation this autumn, that is a quality in short supply.