José Mourinho has spent much of this season praising his players for surviving in difficult circumstances, but an even greater test of their fortitude is to come. Chelsea showed all their characteristic resilience on a stormy night in this harbour city, overcoming the loss of John Terry, their captain, Arjen Robben, his replacement, and an early goal to secure a valuable draw courtesy of an equaliser from Andriy Shevchenko.

For all his misgivings over Mourinho, Roman Abramovich must surely be impressed by the spirit he has instilled into the players, which for the first time appears to have infused the owner’s favourite player. In trying circumstances the Ukraine striker produced his best performance in a Chelsea shirt, working tirelessly, scoring his eleventh goal of the season and creating several chances that were spurned by Didier Drogba.

“Shevchenko was brilliant, absolutely brilliant,” Mourinho said. “The goal he scored is a crucial goal for us, but I’m delighted with the way he’s working for the team. It’s fantastic. His improvement is amazing and everyone is delighted with the way he’s playing.

“In the circumstances we did well. I’m not saying 100 per cent we will beat Porto, but we’re very confident.”

Chelsea will expect to progress at Stamford Bridge, though Terry’s ankle injury could have grievous consequences for the rest of their campaign, particularly in the Barclays Premiership. The 26-year-old began training on Tuesday with strapping on his right ankle, calling into question his selection in the first place.

Although culpable for Raul Meireles’s goal, Michael Essien filled in with aplomb last night, using his pace, strength and seemingly endless energy to compensate for a lack of positional sense, though the captain’s aerial dominance and leadership skills simply cannot be replaced.

Frank Lampard shrugged off a stomach bug to play his part last night, while Robben succumbed in the second half to a familiar muscle complaint, but it is Terry’s loss on only his third start after back surgery that will prove most damaging.

“It’s always difficult to lose a defender so early in the match, especially when you don’t have one on the bench,” Mourinho said. “From that point everything changes. Robben extended them but when he came off we had to change tactics. It was not a beautiful game but I was pleased with the result. We’ve got a lot of problems but are surviving, we’re in every competition and cannot cry.”

Chelsea had begun with a familiar-looking 4-4-2, but their comfortable shape did not survive a frenzied opening. Terry regards playing on through pain with the same indifference as playing in the rain, so when he pulled up after clearing the ball in the eighth minute it was clear he had a serious problem.

With Chelsea’s medical team struggling in vain to get their talisman back on to the pitch they were hit by another blow, as Porto capitalised on the confusion at the heart of their defence to grab the lead. After a jinking run down the left in the twelfth minute, Ricardo Quaresma sent over a cross that was not cleared by Essien and Meireles took full advantage, sending a stunning volley past Petr Cech.

Robben came on for Terry and was the architect of Chelsea’s immediate equaliser, running down the left to put Shevchenko through on goal in the sixteenth minute. The former AC Milan striker was bought for exactly these sort of high-pressure situations and did not disappoint, neatly shooting across Helton for his 45th Champions League goal.

Shevchenko has insisted all along that his poor form was merely temporary and his class may prove permanent after all. Robben continued to provide a useful outlet down the left, but for the rest of the first half Chelsea struggled as another left winger took control. Quaresma gave Lassana Diarra, the right back, a torrid time as he repeatedly reached the byline and it took several saves from Cech to keep Chelsea on level terms. Quaresma also hit the bar with a sweetly struck half-volley.

Robben’s injury forced further changes, with Mourinho bringing on John Obi Mikel to give Diarra greater protection and the plan worked to perfection.

Porto dominated in terms of territory and possession without producing anything to show for it as the visitors dug in impressively. Chelsea even created the better chances towards the end as Shevchenko’s improvement continued. His frustrating partnership with Drogba is finally flowering but for once it was the Ivory Coast striker who let the side down, hitting the post and heading wide after twice being set up by his strike partner.

While Chelsea’s relieved fans belted out Blue is the Colour on the final whistle, a more appropriate anthem for this season would be Gloria Gaynor’s I Will Survive.

FC Porto (4-3-3): Helton — Bosingwa, Pepe, Bruno Alves, Fucile (sub: B Morales, 65min) — L González, P Assunção, R Meireles (sub: M Cech, 55) — L López, H Postiga (sub: Adriano, 77), R Quaresma. Substitutes not used: V BaÍa, R Costa, Alan, J Paulo. Booked: Pepe.

Chelsea (4-4-2): P Cech — L Diarra, R Carvalho, J Terry (sub: A Robben, 13; sub: J O Mikel, 46), W Bridge — M Essien, M Ballack, C Makelele, F Lampard — D Drogba, A Shevchenko (sub: S Kalou, 88). Substitutes not used: C Cudicini, Gérémi, P Ferreira, S Wright-Phillips. Booked: Makelele, Essien, Cech, Ballack.

Referee: M Busacca (Switzerland).