Cristiano Ronaldo's Portugal take on Confederation Cup hosts and Group A leaders Russia on Wednesday with the tax storm scandal clouding Ronaldo's Real Madrid future.
Having opened their Confed Cup campaign with a 2-0 win over New Zealand, Russia face a step up against Euro 2016 winners Portugal and their troubled superstar captain.
Spanish authorities accuse Ronaldo of evading 14.7 million euro ($16.5m) in tax and he has been summoned to appear in court next month in Madrid.
The four-time world player of the year has protested his innocence and has threatened to leave Real over the matter.
President Florentino Perez has said Champions League winners Real have so far received no offers for Ronaldo, the world's highest paid athlete according to Forbes magazine.
Despite the off-field disruption, Ronaldo picked up the man-of-the-match award in Portugal's opening 2-2 draw with Mexico on Sunday.
Having rattled the crossbar, Ronaldo's deft pass in the area found Ricardo Quaresma unmarked to open the scoring in Kazan.
Javier Hernandez then equalised, only for Cedric to restore Portugal's lead late on before Mexico equalised with a header by Hector Moreno from the final corner.
"I was happy to have scored, but sad about the result,” said Quaresma.
"We had enough chances to win the game."
And Russia know the key to derailing Portugal is ensuring Ronaldo has a quiet match at Moscow's Spartak Stadium.
"The first place in group after the first game means nothing," said Russian midfielder Alexey Miranchuk.
"It only matters after three games.
"We saw how dangerous Portuguese counter-attacks can be against Mexico. We must be ready for them."
The hosts will have vocal home support as their captain and goalkeeper Igor Akinfeev is set to make his 100th appearance for Russia.
Portugal's coach Fernando Santos has said he will rotate his team through the Confed Cup.
After Portugal's defensive frailties were exposed against Mexico, Santos could inject some pace in midfield by starting with Gelson Martins, Nelson Semedo and Andre Silva.
Strangely, Portugal have never won in Moscow, losing all three of their previous games there.
The Soviet Union beat Portugal 5-0 in a European championships qualifying match in the Russian capital in 1983.
Then in 2012 Russia won a World Cup qualifier 1-0 against Portugal and ran out winners by the same slender scoreline in a friendly in 2015.