Karim Benzema hit a double, while Emmanuel Adebayor was also on the scoresheet in the 3-1 win.
"You have other options on the pitch when you field two strikers. We have players who are capable of playing in different formations and they responded very well against Racing. Karim [Benzema] and [Emmanuel] Adebayor offered us some great solutions," said Mourinho.
"It's not the first time that I've employed this formation. I eventually decided to play like this, but there were plenty of alternatives. We'll probably return to our usual setup when Cristiano [Ronaldo] returns though."