Iran are third in Group F with one point after a goalless draw with Nigeria and the heartbreak of their 1-0 defeat to Argentina when Lionel Messi scored in added time. (Agencies)
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).
Salvador's Arena Fonte Nova has seen 17 goals in three games after the Netherlands 5-1 romp over Spain, Germany's 4-0 hammering of Portugal and France's 5-2 rout of the Swiss.
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,” he added.
"I hope we have showed the world that Iran can play football,” he said.
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.
The defeat ended Bosnia's first World Cup campaign in the group stages but striker Edin Dzeko wants to sign off in style.
Dzeko was left fuming after the defeat to Nigeria when he was denied an early goal by the linesman's flag but replays showed the player was clearly onside.
The Bosnians claimed New Zealand referee Peter O'Leary then missed a foul on Emir Spahic in the build-up to Peter Odemwingie's 29th-minute winner.
Iran are third in Group F with one point after a goalless draw with Nigeria and the heartbreak of their 1-0 defeat to Argentina when Lionel Messi scored in added time.