Fernando Torres, a £50 million signing from Liverpool in January 2011, was not selected to start the first leg at Parc des Princes, as Mourinho deployed André Schürrle as an auxiliary striker.
PSG, meanwhile, boasted Zlatan Ibrahimović, Edinson Cavani and Ezequiel Lavezzi, who hit a stunning half-volley to open the scoring.
With Samuel Eto'o injured, Torres was eventually introduced but hardly effected proceedings, as Demba Ba remained rooted to the substitutes' bench.
"I'm not happy with my strikers' performances, so I have to try things," Mourinho said. "With André at least I know we have one more player to have the ball, we have one more player to associate with the other players.
"Football is also about scoring goals. That is for strikers, for real strikers. I had to try."
The "real strikers" barb could prove to be the final straw for club-record buy Torres, although Mourinho was scathing in analysing Chelsea's performance, lamenting individual mistakes and Javier Pastore's "joke" third goal.
Mourinho said: "The third goal was a joke. It's not a goal. It's a joke. We enjoyed the third goal with Pastore. The third goal was Pastore and us.
"We made individual mistakes in areas where for the whole season the guys perform and we have no problems. They have the right to make their mistakes, because we have other players that make mistakes the whole season. We paid the price.
"The ball goes to Lavezzi in the first goal, control, half-volley, boom. Top player, top striker. It's like this at this level, one chance, one goal.
"It's difficult for us to score goals. It's difficult for us to score goals, especially when the games are tight. It's difficult for us to transform the half-chances into chances and when you make defensive mistakes you are in trouble. That's, for me, simple."
An Eden Hazard penalty had cancelled out Lavezzi's strike but a David Luíz own goal restored PSG's lead before Pastore struck a pivotal blow in stoppage-time.
Chelsea, beaten by Crystal Palace last Saturday, have now lost three of their last five games after just one defeat in the previous 17.