The 21-year-old was a pivotal figure in Sunderland's remarkable escape from relegation, scoring five goals in three games which catapulted the Black Cats up the league.
However, it was all too little too late for England boss Roy Hodgson, who did not hand Wickham a surprise late call-up.
And it left the former Ipswich striker wondering what might have been, if he had been handed a first-team spot earlier.
"There's part of me that thinks 'that could have been me going to Brazil'," Wickham told the Daily Express.
"Maybe if I had the whole season playing in the Premier League then it could have been different.
"But I'll have a good summer now, rest and work hard for next season.
"My main aim will be to play at Euro 2016."
Sunderland shelled out £8million on a much sought-after Wickham three years ago, but he has taken his time to prove his worth.
And now, feeling part of the regular starting XI, Wickham insists he can kick on.
"Maybe if I had stayed fit and the injury hadn't have happened, then we could be talking about something else," Wickham added.
"The next year will be vital for me. I've got in the Sunderland team now.
"I need to make sure that I am in it every week, and push on and prove to people that I'm no flash in the pan."