Zenit St Petersburg captain Danny threw Andre Villas-Boas' side a Champions League lifeline as his goal earned them a patchy 1-0 victory over Benfica.
Hosts Zenit became embroiled in a nervy Petrovski Stadium encounter with their Portuguese rivals, with both sides at risk of early elimination in Group C.
Former Porto striker Hulk laid on the perfect ball for Portugal midfielder Danny to blast the winner and dump compatriots Benfica out of the Champions League.
The defeat left Benfica facing total elimination from European competition this term if Monaco pulled off victory over Bayer Leverkusen in Germany in the later kick-off.
Jorge Jesus' side were left to lick their wounds from a second straight defeat to Zenit, and then cross collective fingers Leverkusen could deny Monaco.
Zenit's victory meant former Tottenham and Chelsea boss Villas-Boas' side could still qualify for the knockout stages of Europe's top club contest.
The Russians will face Monaco in the final round of group-stage fixtures, where victory could yet push them into the tournament's next phase.
A cagey first half yielded precious few attempts on goal as both sides seemed almost crippled by fear of the repercussions of defeat.
Argentina winger Eduardo Salvio wasted the best opportunity of the half for Benfica however, latching onto Nicolas Gaitan's fine cross only to fire straight at home goalkeeper Yuri Lodygin.
The visitors again took the initiative after the restart, forcing an early spell of second-half territory and possession that put Zenit under pressure.
Luisao squandered the chance of the match when claiming a loose ball and blasting a shot, the Benfica captain aghast to watch his effort threaten to fly out of play for a throw-in.
Luisao's effort was so poor in fact that Benfica managed to retain possession and keep the move alive.
Another chance fell to Jardel rushing onto a right-wing cross for a header, but the defender also failed to hit the target.
Just as the momentum looked to be swinging away from the hosts, Zenit skipper Danny launched a smart move, setting Brazil forward Hulk away in the Benfica box.
Andre Almeida's last-ditch tackle snuffed out the danger though, as the game remained goalless past the hour mark.
The hosts continued to press without any serious penetration, with Hulk blasting a free-kick high and wide after Enzo Perez had fouled Zenit substitute Oleg Shatov.
Just when the hosts feared the breakthrough would never come, up popped Hulk with the pinpoint cross and Danny raced through to do the rest.
Benfica's wretched evening was worsened still further when captain Luisao was sent off in added time for a second bookable offence.