The 28-year-old from Faisalabad was included in Pakistan's 16-man squad for the four Tests and five One-day matches in England after an ankle injury ruled Akhtar out for six weeks.
"It really surprised me when I got a call from Pakistan Cricket Board for my passport, I couldn't believe my ears," Nazir told AFP on Friday.
Nazir, who was not even in the preliminary 21-man squad for the tour, was brought in on captain Inzamam-ul Haq's recommendations.
Nazir hoped his four years of experience in English conditions would help him on the tour.
"I know English conditions well having played Northeastern League and was also part of Pakistan's 1996 team to England. I will do my best to trouble the England batsmen and help Pakistan win.
"I have seen a lot of England batsmen Marcus Trescothick, Andrew Strauss, Andrew Flintoff and Kevin Pietersen on television and will do my best to ruffle them," said Nazir.
Nazir has played only eight Tests since his first against Zimbabwe 10 years ago.
His last outings at international level were tours of India and the West Indies last year as a member of the One-day squad, but he was not required to play in any of the eight matches.
The last time he donned the green Pakistan cap was against Sri Lanka in the 1999-2000 season, but his 49 wickets for Faisalabad and Habib Bank in the last domestic season helped pave the way for a recall.
Nazir said replacing Akhtar was a big challenge.
"Akhtar is a wicket taking bowler and replacing him in the team is a great responsibility but I will fulfill the confidence shown on me by the captain and others," said Nazir.
Akhtar's MRI scan revealed an old ankle injury sustained last year had not healed properly.
Pakistan will start the second phase of their training from Saturday before leaving for England on June 25.
They open the tour with a three-day side match against Leicestershire from July 1 and then play England 'A' in another three-day fixture before the first Test starts at Lord's from July 13.