Chelsea were on course for the Europa League final after a last-gasp victory in Basel that left interim manager Rafael Benitez feeling relieved.
David Luiz was the hero of the semi-final at St Jakob-Park, scoring a driven free-kick with the last kick of an intense first leg.
Victor Moses had put the Blues ahead after 13 minutes but they were unable to add another in regulation time, with wayward finishing, fine goalkeeping and plain bad luck thwarting them.
Chelsea's evening worsened three minutes from time when referee Pavel Kralovec awarded a soft penalty against Cesar Azpilicueta, allowing Fabian Schar to slot home the equaliser.
Clearly aggrieved, Chelsea returned to the attack with renewed vigour and eked out a winner to put them in the driving seat ahead of next week's return leg at Stamford Bridge.
Asked if the 2-1 win was deserved, Benitez said: "Yes, I think we had to work hard until the end.
"I think we had chances on the counter-attack and we couldn't score a second goal.
"After the penalty, which was a surprise for everyone, I think in the end the second goal from David Luiz was good enough for us. But I was a little bit worried about this penalty.
"For us, it wasn't [a penalty]. To give a penalty, it has to be very, very clear."
Having seen London rivals Tottenham exit to Basel in the quarter-finals, Chelsea were well aware of the threat posed by the Swiss champions.
Murat Yakin's team secured 2-2 draws in both of their matches with Spurs and such displays mean Benitez will not be taking Chelsea's place in the Amsterdam finale for granted.
"We have the experience from Tottenham so we know this team is a very good team, who can score goals home and away, so we have to be sure to concentrate," the Spaniard said.
"We can't be over confident in the next game and do our job. We know that, if we play well, we can beat anyone so we can do it.
"It was a very intense game with a high tempo, and we know that we were playing against a side who haven't lost at home.
"They have beaten a lot of teams and played with an intensity that is great for the fans.
"We knew we had to do our job and I think we did it very well.
"We had chances on the counter-attack and might have scored more goals, but we've beaten a good team."
Thursday night's result was not only important in terms of Chelsea's Europa League ambitions but a welcome boost after Luis Suarez earned Liverpool a draw deep into stoppage time on Sunday.
"I hope this is a boost," Benitez said, looking ahead to this weekend's league clash with Swansea.
"We're working so hard, so if you can win these kind of games the mood is much better.
"That will be a different competition, but we have to take the positives and try to keep the momentum."