Russia's two World Cup qualifiers against Portugal will decide the winner of Group F, former national team goalkeeper Vyacheslav Malafeev told R-Sport.
Russia kick off their campaign later Friday against Northern Ireland in Moscow, and then fly to Israel on Tuesday.
But the 33-year-old Zenit St. Petersburg stopper, who quit international football last month to spend more time with his family, said the real tests will come in October and next June.
"I think there will be two decisive matches - the home game in October in Moscow and the away game in June in Portugal. It's clear these will decide the outcome," said Malafeev.
The task is not beyond Russia, he said.
"If everything is given, and the tactics are right, then it's possible to outplay any team."
Russia's other opponents in Group F are Azerbaijan and Luxembourg.
Malafeev has 29 caps for Russia and was the country's first-choice goalkeeper at Euro 2012.
He was left to raise his two children on his own after his wife Marina died in a car crash in March last year.
He announced his retirement from the international scene last month, but stressed his decision was temporary.
New Russia coach Fabio Capello chose CSKA Moscow's Igor Akinfeev to start in his first game in charge, a friendly against Ivory Coast on August 15, which was widely understood as a signal that Malafeev would revert to a substitute role.