In Salvador, the Iranians must beat Bosnia, who are already out, while hoping Nigeria fail to pick up a point against Argentina in Porto Alegre, which also kicks off at 1300 local time (1600GMT).
Iran can now do with scoring a few of their own at the same venue.
If they win and Nigeria loses, both sides will finish with four points leaving goal difference to decide who goes through to the last 16 clash in Brasilia next Monday against the Group E winners.
Fulham's Dejagah says his side must bounce back from the disappointment of their Argentinian defeat with a win.
"We still have a chance to go through and who would have thought our World Cup would last longer than England and Spain," Dejagah said.
"We had such a bad feeling after the match against Argentina because of the way it ended.
"We tried to make it tough for them and with a little bit of luck we would have won this game or even got a draw.
"I hope we have showed the world that Iran can play football."
The Bosnians are on their way home after losing their opener 2-1 to Argentina and then 1-0 to Nigeria on Saturday, but Safet Susic's side want to bow out with heads high.
"We're going into this with a deep desire to finish in an honourable way and earn some redemption for our defeats," said Susic, who will reveal his future as head coach in the next ten days.
"We were expecting this to be our key match for the round of 16, but things haven't panned out how we wanted.
"It's important to bid farewell to the World Cup in a nice manner."
The Bosnians are still smarting from their Nigeria defeat.
Striker Edin Dzeko was denied an early goal by the linesman's flag, but replays showed the player was clearly onside.
"We should have won the game, but the referee was shameful," said Manchester City's Dzeko said.
"We know that we are not going into the next round, but we will try to do our best in the next game," pledged Dzeko.
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- Ashkan Dejagah
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