Above all else, parity remains in the tie.
But it's not that simple. The limited scope of Chelsea's intentions at the Vicente Calderon represents a huge gamble for Mourinho and his team. It is one thing defending stoutly at home in the first leg of a Champions League tie before attempting to nick the second, it is another thing altogether to attempt the pattern in reverse.
Mourinho has won the Champions League twice - with Porto and Inter - and on those occasions he played every first-leg knockout tie at home. He knows how to win the tournament but he has never done it in this order.
Chelsea have taken heart from their 0-0 draw but Atletico, despite failing to erode those English foundations, will be more pleased with the outcome.
A home clean sheet is the most important element in any Champions League knockout tie. In the quarter-finals, three of the four teams who went through avoided conceding in their own back yard. That zero beside Chelsea's name rather than the one next to Atletico's counts for more.
Atletico, themselves, are not an electrifying team. This was not a just case of Chelsea stifling them and disrupting the rhythm of their game. In honesty, they lacked the guile and intuition to break down what was in front of them. It showcased their attacking limitations when faced with a puzzle like Mourinho set.
They will, however, be far more comfortable in the atmosphere of the second leg when the onus, however more slightly, will be on Chelsea to come out and play. Diego Simeone's chief strengths are not those passes at the edge of the area, probing for that one golden chance like Bayern Munich or Barcelona.
They enjoy being on the other end of that, soaking up pressure in their well-drilled back four before hitting with the promptness and accuracy of their midfield work. Their results against Real Madrid and Barcelona this season will testify to that.
Of course, we could very well receive more of the same from Mourinho at Stamford Bridge. He will be without Frank Lampard and Jon Obi Mikel, suspended, and Petr Cech, who suffered a dislocated shoulder. John Terry, too, will be doubtful, while there are no guarantees of Hazard or Eto'o's participation.
Penalties at the end of another gruelling 0-0 draw and extra time could well be looming. His Chelsea teams have scored only one goal in all their five of their Champions League semi-final matches now.
Atletico are a team who have specialised on agitating esteemed opponents this season. One meaningful swing of Diego Costa's boot at the Bridge could render all Chelsea's efforts in Spain worthless.
Fans will tolerate dour football so long as trophies are forthcoming. But if Chelsea fail to shut out Atletico again? Well, even a worm will turn.