Stamford Bridge, once again, feels like a happy place to be. It has been a difficult, frequently ignominious season and there was a point last night, almost inexplicably, when it seemed there could be one more excruciating low, but the team deserve their place in the semi-finals despite the late scare when everything threatened to go horribly wrong.

Chelsea had led through Frank Lampard's 21st-minute penalty and really ought to have made more of their chances after Maxi Pereira had been sent off five minutes before the interval. Javi García's late, jolting equaliser, with a free header direct from a corner, would have been a terrible goal to concede at any time and, after 85 minutes, it sparked something that strayed dangerously close to panic.

Benfica had played far more impressively than at the Estádio da Luz last week and there were moments in a nerve-shredding finale when they threatened a second goal to eliminate their hosts. John Terry had left the pitch with suspected cracked ribs – he will undergo a scan in the morning – and the 10 men of Benfica sensed something remarkable when they won a free-kick, two minutes into stoppage time, and sent just about every available player into the penalty area.

As it turned out it was a poorly taken free-kick, headed out by Mikel John Obi. Raul Meireles took the ball off Yannick Djaló and drove forward into a vast expanse of space where the Benfica defence had previously been located. It was finished with a torpedo of a shot, still rising as it hit the net. The relief was immense.

Whether this team are capable of getting past Barcelona over two legs is another matter. They will certainly have to play much better, tighter at the back and less generous with their finishing. More than anything they will need to show a greater sense of control and, even then, it is difficult to get away from the fact that their opposition appear to belong to a different universe sometimes.

Roberto Di Matteo's team struggled at times to get any momentum, particularly early on when they were careless enough for Terry to remonstrate angrily with his team-mates. Equally, it should not be overlooked that Benfica came into the match missing four centre-halves because of injury, including the two Brazilians, Luisão and Jardel, who had played in the first leg. García, a midfielder by trade, and Emerson, a left-back, filled the roles and Axel Witsel, another midfielder, was moved to right-back after the sending-off. With such an experimental back-four, it is not surprising they were vulnerable.

The penalty, for example, originated from an error of positioning from García after Ashley Cole had surged forward from left-back. The Benfica player was caught the wrong side of his man and it was a clear barge as he tried to prevent his opponent from getting into a shooting position. Lampard's penalty was struck powerfully to the right of Artur, though he was a little fortunate that it went under the goalkeeper's right glove.

Benfica had been on top at the time, playing with a mixture of adventure and belief, and they responded well to the opening goal. Ultimately, however, the red card left them with too great a disadvantage, and they made little attempt to conceal their disgust at Damir Skomina's refereeing.

Skomina's last visit to London was the Arsenal-Milan tie that resulted in Arsène Wenger receiving a three-match ban for berating the Slovenian at the final whistle and then criticising him after the match. This time it was Jorge Jesus, the Benfica coach, who could barely contain his ire. Skomina showed five yellow cards plus two for the sending off in the opening 45 minutes, which was totally out of keeping with the game. Five of the yellows had gone to Benfica players. All the same, their complaints were undermined because Pereira, as one of them, was reckless to raise his studs when challenging Mikel.

Benfica could have waved a white flag at this point. Instead they began the second half as they had the first, pressing forward, with Oscar Cardozo always a difficult opponent, just as he had been in Lisbon. Cardozo could reflect on two Petr Cech saves and a goalline clearance from Terry before he was withdrawn. Yet the second half was mostly a story of squandered Chelsea chances – more, in truth, than Di Matteo will want to remember. Ramires somehow missed from a yard when it seemed easier to score. Fernando Torres had a busy match but his finishing was always skew-whiff. Juan Mata was the same.

Perhaps a bit of complacency crept in, too, as Benfica lost their momentum for a 20-minute spell and the crowd serenaded Di Matteo. It certainly seemed that way with the defending when García headed in Pablo Aimar's corner.

It was a soft goal, and there is no way Chelsea will get away with that kind of generosity against Barcelona.