The South African was a key member of England's backroom staff last summer and saw first-hand how the Durham seamer struggled to deal with the pressures of the international game, and he is concerned that those fears - combined with a lack of understanding about just what made Harmison the planet's top bowler at one point - could spell the end.

"I've never seen a bloke as low as Steve was during that Manchester Test against West Indies," Donald told the Daily Mirror. "When he came off the field he admitted he was dead scared."

He added: "He was scared of letting the ball go and he soon realised that Michael Vaughan could not turn to him.

"Sometimes I feel that there is a fear of being on that massive stage. It could be."

Donald added: "Does he know and fully understand how he became the world's number one bowler? Or did he just bowl?

"I had my doubts as to whether Harmy really understood how he had got there. That's why inconsistencies creep in."