Chelsea 2 FC Porto1/Chelsea win 3-2 on aggregate:Jose Mourinho escaped the Champions League defeat that would have hastened his departure as Chelsea's manager.

It was fitting that the man whose goal would decide this pulsating encounter should be Michael Ballack, the man in whom he had placed his faith amid so much criticism. After hinting on Monday he would not be long of west London, Mourinho is setting about his legacy in this competition. It could yet be engraved on the European Cup.

Mourinho had spoken of his "prize motivation", how the fact he would be in the Champions League's quarter-final and the FA Cup semi-final "in five days" was driving him. Of course, it did not occur to the Chelsea manager that his team might not overcome Porto and Tottenham between last night and Sunday.

Having taken an away goal from the 1-1 draw in the first-leg trip to Porto, Mourinho's confidence seemed well placed. Until Ricardo Quaresma struck to annul that advantage only 15 minutes in, that is.

Defending higher up the pitch than they are accustomed to do with the missing John Terry in their midst, Chelsea have become vulnerable to the long pass and Porto were alive to its potential.

With Claude Makelele too often static in the centre of midfield, Porto were passing it round him, a weakness that was compounded by Michael Essien's error. The Ghanaian seemed to forget that his role last night was as a central defender and not as the dynamic midfielder so beloved of Chelsea's fans.

Already advanced as high as the halfway line, Terry's replacement pulled further away from his central-defensive partner Ricardo Carvalho and was sucked in to challenge Lucho Gonzalez. Essien was scrambling back to his post but the gap between him and Carvalho was wide enough for lesser talents than Lucho to play in a perfectly measured pass.

Quaresma advanced on to his through ball and slipped it under Petr Cech to electrify this game.

Chelsea seemed to be crackle nervously at the shock. Ashley Cole made an overlapping sprint up the left wing, searching for a return pass from Frank Lampard. But the England international played the ball into the hoardings, prompting Mourinho to rise from his seat and beseech his players to be calm.

Lampard, though, was uncharacteristically hurried every time the ball reached him. The most costly such occasion was on the half hour, when Andriy Shevchenko's centre found him eight yards out but unable to capitalise.

Arjen Robben, who had made several spearing runs at the Porto defence, was similarly unable to make the most of the available time when, shortly before the interval, he set himself up on the edge of the area but shot well wide. There was resilience from Porto, too.

Cole's low cross for Shevchenko presented a fine chance close in but Ricardo Costa's brave challenge denied the Ukrainian his shot just as he opened up his body to pull the trigger. The secondary chance that fell to Didier Drogba was scooped over.

And all the while Chelsea's midfielders were giving the ball away too cheaply.

Mourinho addressed the possession problem by withdrawing Makelele for John Obi Mikel at the interval, but the Nigeria international had no hand in the goal, which instantly followed the break. Diarra pushed into the outside-right channel, dragging it back for the ubiquitous Robben. The forward's speculative effort, from all of 25 yards, had Lampard and Shevchenko following up in hope. Helton had his near post well covered, but the goalkeeper somehow contrived to allow the ball to bobble over him for the equaliser.

From that moment, each time the ball approached Helton, who had twice dropped or ducked crosses, he was subjected to mocking that seemed utterly to unnerve him. It all added to the growing drama. Something would have to give.

Then, 11 minutes from time, Cole's high, diagonal ball found Drogba on the edge of the area. His header across goal for Shevchenko was returned to Ballack, who clinched the tie with a hooked shot from close in.

CHELSEA:Cech, Diarra (Ferreira 65), Essien, Carvalho, Ashley Cole, Makelele (Mikel 46), Robben, Ballack, Lampard, Shevchenko (Kalou 84), Drogba. Subs not used:Hilario, Boulahrouz, Bridge, Wright-Phillips. Booked:Robben, Diarra.

FC PORTO:Helton, Fucile, Pepe, Bruno Alves, Cech (Ibson 55), Gonzalez, Ricardo Costa, Paulo Assuncao, Raul Meireles (Adriano 55), Lopez (Bruno Moraes 82), Quaresma. Subs not used:Vitor Baia, Alan, Postiga, Joao Paulo. Booked:Quaresma, Fucile, Adriano.

Referee: Roberto Rosetti(Italy).