Chelsea are no better than 50/50 to beat Atletico
It is a tie with sub-plots galore and the one Chelsea would have chosen but they should consider their semi-final progress as far from inevitable.
The sub-plots could hardly be more numerous. Jose Mourinho back in Madrid. Another manager, Diego Simeone, ready to prove himself as the outstanding young coach in Europe.
Fernando Torres returning to the club he grew up supporting. Diego Costa facing the team he is likely to join and Thibault Courtois going up against his parent club.
The previews might write themselves but we should still be wary of thinking that the script has also been decided in Chelsea's favour.
Yes, it probably is the draw that Mourinho would have chosen but, on recent form, it is still no more than a 50/50 match.
Atletico Madrid are top of La Liga just now for a very good reason. They defeated Barcelona to reach this semi-final for an equally good reason. It was also no accident that they should beat Mourinho's Real Madrid in the final of last year's Copa del Rey, or that they also won both the Europa League and European Super Cup in 2012.
They are, despite annual revenues that around one third those of Chelsea, an excellent team with a fanatical support-base that has been inspired and mobilised over the past three years by Simeone. Few inside the Estadio Vicente Calderon on Wednesday night would regard Chelsea's progress to a third consecutive European final as inevitable.
"With these fans it's impossible to lose," said the midfielder Koke, after the Barcelona victory. Everything, though, flows from the work of Simeone and how he has performed the remarkable trick this season of improving his team even after being forced last summer to sell his best player in Radamel Falcao.
The transformation of Costa, who originally arrived for only £1.5m in 2007, into the most sought-after young striker in the world is indicative of a culture of self-improvement.
João Miranda, a free signing from Sao Paolo, has been outstanding. Adrián, an Austrian striker, has covered superbly at times this season for Costa. Gabi, the captain, has resurrected his career. Koke now looks like a natural successor to Xavi, Iniesta, Busquets and Alonso in Spain's formidable tika-taka midfield.
Courtois, always regarded as an outstanding prospect by Chelsea, can already be listed alongside Petr Cech as one of the best goalkeepers in the world. Atletico, after all, have conceded only five goals in the entire Champions League this season.
With Koke and Costa certain to attract huge offers this summer, and Courtois returning to Chelsea, there is very much a sense that Atletico must seize this moment.
It is 40 years since they were last in the semi-final of the European Cup. Their debts are estimated at £80m and it is inevitable that Simeone will be offered the chance at some stage to work at a club that can provide him with rather more resource.
Simeone's response to a question on Wednesday about Costa's future still gave a telling insight into the club's mentality. "Surely he's not going to find a club like this one?" he said. "We can envy other teams' economic power but, when it comes to competing, we don't envy anyone anywhere."
Mourinho's experience of losing in a major cup final last year to Atletico should guarantee there will be no complacency. The past record both of himself - this is his eighth Champions League semi-final in 10 attempts - and Chelsea - their seventh in 11 years - should also prove advantageous. Chelsea can again be expected to find a way to win but it will be close.