MICHAEL Vaughan has outlined the importance of a successful tour of South Africa for under-pressure batsmen Alastair Cook, Ian Bell and Paul Collingwood.

Vaughan led England in their 2004-05 campaign success against the Proteas and he believes the trio are playing for their futures on the international stage.

He said: "Over time they will have to score big runs, and the likes of Bell, Collingwood and Cook know that this is a big tour for them.

"You are only one tour away from being great and only one tour away from being in the doldrums.

"Those three players will know this is a big tour for them.’’ Vaughan is optimistic England can build on their success over Australia and present a challenge to a team recently ranked the best in the world before they were overtaken by India.

He added: "I think they have a good chance.

"(Captain) Andrew Strauss and (coach) Andy Flower have created a good environment within the dressing room which takes some doing.

"Beating Australia in the summer will add pressure as the country expects them to move on from that.

"If we want to be perceived as a team on an upward curve we have to go to South Africa and compete.

"Whether we can win...that will be tricky but we have to compete and make the South Africans know they are in a contest.

"We have a number of young players who have played a few games now, Cook, (James) Anderson, (Stuart) Broad, (Matt) Prior, (Graeme) Swann.

"They can't be seen as inexperienced Test match players any more so they have to go on to the next level.’’ He added: "You have to win the key moments. Bowling South Africa out twice will be the biggest problem.

"If you look at the times when we have struggled to bowl out opposing sides it is when the ball isn't swinging.

"Their batting line-up is one of the best in the world, they get big hundreds when they get in.

"If we get runs on the board we have a chance but getting 450 runs on the board will be equally difficult.’’