England have surprised Australia with their combative and confident brand of cricket. Stephen Harmison and Andrew Flintoff have consistently troubled the visitors' batsmen and, unlike England teams of the past, they have recovered from dire positions and remained competitive.
Vaughan has every right to feel that the tourists are vulnerable, and that they can be beaten. But in turn Ricky Ponting, his Australian counterpart, must already be sensing that England will struggle to defeat his team should they play as they did on Sunday.
The losing captain will attempt to convince everyone that the result of the game has no bearing on the first Test, which starts in nine days' time. But, after fulfilling his media obligations, you can be sure that he would rather be returning to the dressing-room situated 20 yards away from the one where his kit sits.
It has taken some time but Australia are beginning to come to terms with the approach of their opponents. Ponting's brilliant innings of 111 on Sunday could not have come at a better time, and Brett Lee's 5 for 41 means that three Australian bowlers - Glenn McGrath and Shane Warne are looking worryingly good - will arrive at Lord's in next week full of confidence.
With the exception of the Twenty20 match, which is not a proper game of cricket anyway, England have started poorly in the field in every game. In four of the seven limited-overs matches Vaughan has been forced to withdraw one of his opening bowlers from the attack before the seventh over.
In each game the Australians have raced along at more than four runs an over before losing their first wicket, and on a couple of occasions the run rate has been as high as seven. But having grabbed the initiative Australia, through sloppy cricket, have allowed England to get themselves back in the match.
Harmison and Flintoff have bowled with hostility and the pair have exploited Australia's ability to self- destruct. Gilchrist is the most culpable of the visitors' batsmen. The destructive left-hander has reached 18 in each innings but failed to go on and win a game for his side.
Vaughan cannot expect Gilchrist's, or Australia's, generosity to continue. It would also be wrong for him to expect Harmison and Flintoff to get his side out of trouble on every occasion.
They need support, and it is difficult to see where it will come from. England have used nine bowlers against Australia but the remaining seven have claimed only 18 of the 43 wickets taken, with two being run-outs.
In one-day cricket, a game where you can win a match without taking a wicket, this predicament can be overcome, but in the Test matches it will become a huge problem. Harmison and Flintoff never shirk their responsibilities but Vaughan will increase the risk of injury should he continue to bowl the pair as much as it appears he will need to.
The one encouraging thing to come out of Sunday's seven-wicket defeat was the batting of Flintoff. The Lancashire all-rounder has not looked his authoritative self during the first three months of the season, but there were several trademark Flintoff strokes during his 87.
"This is a massive game for us," Flintoff said. "It is important we play well as a team. I am yet to play a Test match against Australia and I have only played a handful of one-day games against them so I am excited. Australia are still the best side in the world and we are trying to chase them down. We can go some way towards doing that this summer."
England will be tempted to change their side, but in a match of this importance they are unlikely to gamble. Vikram Solanki's occasional off-spin could be used at The Oval and this should ensure that he keeps his position as substitute. The concept of substitutes has already been written off as folly by some individuals, but good teams and good selecting ensures that all eventualities are covered.
The confidence of Jason Gillespie is Australia's only concern, and Brad Hogg would appear to be the ideal substitute. If Gillespie proves expensive he could be replaced by the left-arm spinner, who could enjoy The Oval's turning pitch.
* England's success over the past 18 months has helped secure a new four-year sponsorship deal with Vodafone that will end after the 2009 Ashes series.
Four players fighting for a place in the Ashes
* DARREN GOUGH
After taking only nine wickets and conceding almost five and a half runs an over during eight NatWest matches Gough is lucky to be holding on to his one-day place. The Aussies have targeted him and won. Gough needs a good performance today or this could be the last time we see him wearing an England shirt.
* KEVIN PIETERSEN
Today's game offers the Hampshire batsman one last chance to impress. After three majestic centuries in South Africa, and an unbeaten 91 in England's first one-dayer against Australia, he appeared destined to be at Lord's on 21 July. But two insipid innings against the world champions has placed a question mark next to his name.
* ADAM GILCHRIST
Australia's dynamic one-day opener has reached 18 in each of his six innings against England, but he has yet to go on and post a half-century. For a batsman of Gilchrist's class this is disappointing. Has batted only once for more than 15 overs - and that was for 15.3 overs in the NatWest series final - and he owes his side a decent score.
* JASON GILLESPIE>
England's treatment of the fast bowler has highlighted what a ruthless game cricket is. Michael Vaughan's batsmen took to him in the Twenty20 match, and his confidence took a further hit during Bangladesh's astonishing win over Australia. The 30 year-old needs to play today, and bowl well, if he is to retain his place in the Test side.Reuse content