Roy Hodgson opted for the 18-year-old rather than Cole, a move that saw the Chelsea defender - capped 107 times for his country - announce his international retirement.
|66/1||Luke Shaw is 66/1 with Paddy Power to score England's first goal at the World Cup|
"I was very surprised," he told reporters. "With Ashley Cole not playing many games [for Chelsea] I thought I may be in with a chance. But I think he played the last three games in the season and he played incredibly well.
"It made me think that maybe this is not my time, but obviously I saw I was announced in the squad and it was the best feeling in the world.
"I don't really feel pressure. I just focus on my own game. I have come here to help the England team and I will do everything I can.
"I feel ready if Leighton does pick up an injury. I don't think Roy would have picked me if he didn't think that."
Shaw made his England debut in the 1-0 win over Denmark in March when he came on as a second-half substitute for Cole.