The England international is in talks over a new Manchester United contract, and the Spain star is looking forward to setting up plenty of goals in future for his new team-mate
Rooney is understood to be in talks over a big-money contract which would keep him at the club for the long term, after Chelsea had an approach for the striker rejected earlier in January.
The England international is back in training following an injury, and Mata is eagerly anticipating the chance to "connect" with the striker.
"For me he is one of the best players in the history of this country," Mata told reporters at his unveiling. "He's an unbelievable player - he can score and he can assist - and I will try to connect with him as much as I can.
"I think that's my best way of playing - trying to find the gaps in defences, to be in the positions I need to be in to assist the strikers."
Robin van Persie and Marouane Fellaini have also returned to training after injury as United attempt to climb the Premier League table in the second half of the season.