Blazevic said Bosnia would be more adventurous when they host Portugal at the Bilino Polje ground. A Bruno Alves header gave Portugal a 1-0 win in Lisbon.
"It's hard to predict anything in football but we will go through in Zenica," Blazevic told Bosnian media after seeing his side hit the woodwork three times in the first leg.
"We can't go through if we play like we did in the first leg, but the return match will be a completely different game of football and we will apply a new strategy to surprise Portugal.
"We deserved more from the match in Lisbon, I've never seen luck turn its back on a team like it did on us but we can turn this round none-the-less."
Edin Dzeko headed against the bar and strike partner Zlatan Muslimovic fired the rebound onto the far post in the 89th minute after Senijad Ibricic rattled the woodwork in the first half.
The Bosnians, who soaked up plenty of pressure before Alves headed the winner in the 31st minute, will miss three key players in the return leg through suspension after Emir Spahic, Elvir Rahimic and Samir Muratovic were booked.
"It will be a very difficult return leg because we will be short of three very important players but I hope we will have more luck than we did in the first game," Dzeko said.
The winners of Europe's four play-offs will qualify for next year's World Cup finals in South Africa and Bosnia are aiming to reach their first major tournament as an independent nation.
They reached the play-offs after finishing runners-up in Group Five behind European champions Spain.
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