Cook celebrates the first half of his double hundred against Australia in September © Getty Images Enlarge

Alastair Cook has been called up to the England squad as cover for Michael Vaughan. A decision on Vaughan's knee injury has been delayed further with the medical team in England recommending that he rests, but he is rated as "very doubtful" for the first Test in Multan.

Cook, the 20-year-old Essex left-hander, who struck a double century against Australia last summer, is a former England Under-19 captain. He was named in the ECB Academy intake for this winter and toured Sri Lanka with England A last year.

David Graveney, the chairman of selectors, said: "Alastair Cook has been called into the squad as we felt we needed an opening batsman to provide cover not only for Michael Vaughan, but also for Andrew Strauss who is expected to fly home before the third Test to attend the birth of his child."

His rise has been meteoric since he was tipped by many as a future England opener when he started breaking batting records at Bedford School. Former England and Essex captain Keith Fletcher called Cook "just about the best young batsman I have ever seen" when he started to make his presence felt in the Essex 2nd XIs. He averaged 48.03 in the County Championship in 2005, hitting four centuries.

"Never in my wildest dreams did I think I'd been heading to Pakistan," he told BBC Sport. "I'm very excited about it and can't wait to get together with the rest of the squad. Peter Moores is doing a fantastic job [at the ECB Academy] and having been there for a couple of weeks I was just starting to feel the benefits."

The England coach, Duncan Fletcher, said that initially England were interested in Owais Shah and Robert Key if a replacement was needed. However, both players have recently undergone surgery meaning that Cook has been handed an unexpected opportunity to get his experience with the full England squad. "It's unfortunate for Vaughan to be injured but a great opportunity for me and I will make the most of it," he said. "David [Graveney] told me I was going as cover for Vaughan and to enjoy it."

An ECB statement said that the medical team will continue to assess Vaughan's condition and a decision on his availability for the second and third Tests will be made in due course.