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.
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.
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.
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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.
"I hope we have showed the world that Iran can play football.