According to Sky Sports, Mourinho's response was simply: "I don't want to talk about it."
However, it was his little aside that shifted the focus to Rooney as he remains out of the country on warm-weather training:
"You have to ask him (Rooney). You have to ask the player. And Man. United because Man. United has a contract with the player that doesn't end at the end of the season."
As reported in the Telegraph, Mourinho is hoping that he can lure Rooney away from Old Trafford at the end of the season. With United currently in seventh place in the league, out of one domestic cup and behind in another, spending next season at Chelsea is currently an attractive proposition.
Chelsea are in need of goals and Rooney would be a good option. However, Mourinho knows that he could land him at a reduced rate in the summer if United's form continues to slide.
The January window is renowned for panic buys and overpaying, neither of which will interest Mourinho. His current squad is good enough to compete with any team in the league, and with no team pulling away in the title race, he can afford to take his time.
United, meanwhile, will not be looking to sell the 28-year-old. He has been one of the lone bright spots in a difficult campaign—although he hasn't played since New Year's Day—and David Moyes needs him.
If United were to sell Rooney in January without investment in top players, Moyes will lose a lot of support from the fans. There's no way that Rooney will leave during the current window and Mourinho knows it.
It's really a non-story at this point, but Mourinho will work it to its fullest potential by refusing to comment and deflecting the attention away from his own club.
The Portuguese manager is adept at mind games and uses the press to his advantage well. Knowing that there is already pressure on United—and with Rooney unavailable for comment—his words were carefully chosen.
When Rooney returns—for the Chelsea game, no less—there will be much clamouring for comment about his future, which will be distracting ahead of the match itself and give Chelsea the advantage.
Leaving Old Trafford in January would be disastrous for United, but Mourinho knows this. He is only concerned with the three points up for grabs when the sides meet.
With Robin van Persie still unavailable, Mourinho knows that Rooney is the key for United when they come to London on January 19. If he can take Rooney's mind out of the game, he has already won half the battle.