Alex McLeish and Rangers could hardly have gone into the match under more pressure or scrutiny after an instantly forgettable performance and result at Falkirk last Saturday.
However, they dragged themselves off the floor and produced a fantastic display of character and quality to claim three vital points in Group H.
Twice they had the lead, twice they were pegged back but Kyrgiakos – the man who only returned just 48 hours before the signing deadline – won the game with a towering header.
As Alex McLeish said before the game, Rangers seem to do things the hard way but this was a night to savour for the manager.
And in the opening moments of the contest it looked like it might be a difficult night as the skilful Portuguese side came out of the traps full of invention and energy.
In fairness to Rangers, Franny Jeffers had started to link well by this stage and Peter Lovenkrands had also served notice that he was in the mood.
In 13 minutes the Danish winger burst away from Pepe and found Jeffers in the box with a great cross. Jeffers should have hit the ball first time but tried to take a touch and that gave Costa time to make a tackle.
Rangers were still vulnerable at times, and Ronald Waterreus had to race from his line and save with his feet as Jorginho threatened to pounce.
However, the more the game went on the more Barry Ferguson became a massive influence.
He started to control things in midfield and he was partially responsible for Rangers taking the lead in fantastic style after 34 minutes.
Alan fouled debut boy Olivier Bernard in a deep position and Ferguson tried to pick the big men out in the box.
His dead ball was cleared as far as Rodriguez who found Ricksen on the right side. The Dutchman looked up and launched a great ball into the box which dropped perfectly for Lovenkrands who lashed a fabulous left foot shot into the right corner.
Ibrox went mad and Lovenkrands rightly celebrated in style.
Dado Prso was in the wars two minutes later when he clashed heads with Pedro Emanuel who had to come off as a result. The Croatian was booked for his part, which seemed slightly unfair.
Porto were certainly unsettled now and Rangers might have had a penalty just before half-time.
Ferguson’s ball over the top seemed perfect for Jeffers and he was bundled to the ground by Pepe as he prepared to take aim.
Remarkably Dutch referee Jan Wegereef took no action. Worse than that Pepe gave Porto an equaliser two minutes into the second half.
The last thing Rangers wanted was to concede early but they were caught out by a near post corner from Peixoto as Pepe got above Hamed Namouchi to head the ball past Waterreus.
There was another blow when goal hero Lovenkrands had to go off with a knock in 55 minutes and he was replaced by Thomas Buffel.
A minute before that the Light Blues nearly responded in the perfect manner when Prso somehow got a cross in from the right and Jeffers connected with his right boot but Vitor Baia made a good save diving to his left.
However, the Rangers fans only had to wait three more minutes before McLeish’s men stormed ahead again.
Costa fouled Jeffers on the right side around 40 yards out and Ferguson delivered the free kick to the back post where Kyrgiakos won it.
Namouchi flicked it high towards the goal-line and Prso bundled the ball over the line with his thigh.
It might not have been pretty but the Ibrox fans could not care less as the roared their approval.
It was just what Rangers needed but, alarmingly, they were caught out again from a corner kick in 71 minutes as Porto drew level again – and it was Pepe who got the goal.
Everyone seemed to miss Peixoto’s corner from the left and in the end it deflected off Pepe’s chest and agonisingly into the net.
Nacho Novo came on for the tiring Namouchi and then Thompson replaced Jeffers, who had worked superbly all night, as Rangers chased a winner.
Surely there could not be another twist to this remarkable contest? There was.
The returning Greek giant Soto Kyrgiakos produced a fantastic finish with six minutes to go to claim an amazing victory.
Ferguson’s free kick from deep was perfection and with a flick of his head Kyrgiakos guided the ball past Baia for a sensational winner.
Next stop, the empty San Siro!
RANGERS: 25-Waterreus; 2-Ricksen, 16-Rodriguez, 14-Kyrgiakos, 3-Bernard; 26-Lovenkrands (4-Buffel 55), 6-Ferguson, 24-Murray, 31-Namouchi (10-Novo 71); 21-Jeffers (19-Thompson 83), 9-Prso.
Subs not used: 1-Klos, 5-Andrews, 8-Rae,18-Pierre-Fanfan.
Bookings: Prso (36)
PORTO: 99-Baia; 14-Pepe, 3-Ricardo Costa, 4-Pedro Emanuel (22-Sonkaya, 40), 21-Cesar Peixoto; 8-Lucho Gonzalez, 20-Diego (7-Quaresma 64), 6-Ibson; 17-Jorginho, 19-Sokota (39-Almeida 64), 27-Alan.
Subs not used: 31-Ribeiro,11-Lisandro Lopez, 18-Assuncao, 35-Cech,.
Bookings: Lucho Gonzalez (45 + 1), Almeida (73)
Ref: Jan Wegereef (Holland)
Man of the match: Barry Ferguson