Diego Forlan blasted Manchester United into the knock-out phase of Europe's most prestigious competition with his 85th-minute winner and Ferguson must now hope the fresh legs of Roy Keane, Ruud van Nistelrooy and the Neville brothers will lead a similar trek to victory in the vital Premiership encounter with Chelsea.
Despite claiming yesterday he would field his best available side against the Greek Group E basement dwellers, the United boss opted to leave three of his key men on the bench and kept them there even though his team struggled to break down the home side in a drab encounter.
Although United enjoyed most of the possession and created a couple of opportunities after the break, the game looked to be heading for a goalless stalemate until substitute David Bellion spotted Forlan's well-timed run into the Panathinaikos box.
The former Sunderland man laid off the perfect pass to the Uruguayan, who found the net for the fifth time in his last six United starts, although Antonis Nikopolidis will wonder how the shot crashed off his legs and into the gaping goal. The pre-match atmosphere was some way below the standard expected of the notoriously vocal Greek supporters and their sense of foreboding proved well founded by an opening period which produced just a single shot on target.
It came from Forlan just before the half-hour mark, but his bobbling 25-yard effort was turned round the post by Antonis Nikopolidis.
If it was excitement the fans were after, they had come to the wrong place. In patches, Cristiano Ronaldo, one of five changes to the side that defeated Blackburn on Saturday, dazzled but there was little else to enthuse over.
Ronaldo might have set up the perfect ending to a flowing five-man United move but drilled his cross between Forlan and Kleberson.
The Portuguese youngster then left Markus Munch for dead outside the Greek penalty area but his floated far-post ball was nodded away by Giorgos Seitaridis before Giggs could reach it. Rene Henriksen had earlier done well to prevent Darren Fletcher latching onto a Giggs cross in the only other noteworthy first-half attack.
There was a worrying moment for United five minutes after the re-start when Rio Ferdinand went down in a heap after clattering into the back of Angelos Basinas.
The challenge was bad enough to earn the England defender a yellow card, but happily for United there was no lasting damage Goalmouth action increased after that incident, although in truth it could hardly have reduced.
Tim Howard and Nikopolidis made comfortable saves from Joel Epalle and Kleberson respectively, then some excellent close control from Giggs created another chance for Forlan which the striker drilled just wide.
Giggs was presented with an even better opportunity shortly afterwards by Ronaldo but the Welshman, captain for the night in Keane's absence, fired wide at the near post.
After his recent stint on the substitutes' bench, Nicky Butt was not doing much to enhance his claims for a permanent recall. He made his usual quota of crunching tackles but his generally neat passing game was missing and he was grateful to Ferdinand's last-ditch intervention after a wayward ball threatened to let in Michalis Konstantinou.
Mikael Silvestre was hurt in a challenge with Joel Epalle late on, although, like Ferdinand, he was able to finish the game, which, with Sunday in mind, was even more important than the win itself.
PANATHINAIKOS: Nikopolidis, Seitaridis, Henriksen, Goumas, Munch, Sanmartean (Epalle 45), Basinas, Zutautas, Maric, Konstantinou (Vlaovic 75), Papadopoulos (Sapanis 83).
MAN UTD: Howard, O'Shea, Ferdinand, Silvestre, Fortune, Fletcher (Bellion 74), Kleberson, Butt, Ronaldo, Giggs, Forlan.