The England forward has scored seven goals in 15 games for the Red Devils in 2013-14 and the centre-back thinks that he is starting to really shine thanks to regular football.
"I just think with Wazza, if he's playing continually - week-in, week-out - with no injuries then you get a fit, striving, thriving Rooney," Ferdinand enthused to the Daily Mirror.
|ROONEY RUNNING RIOT
|ROONEY'S SEASON SO FAR
GAMES AS SUB
"He seems like the old Wayne Rooney. He's happy and he's enjoying his football. You can see his tail's up.
"We have two unbelievable match-winners in him and Robin [van Persie]. We're lucky to have them. When you have two like that who can win you a game by themselves, you just need the other people to play their part and you can be successful."
Ferdinand is not sure, however, whether he will be able to play on past this season, as he becomes increasingly frustrated by the limitations of his ageing body.
"The manager just didn't play me [against Arsenal]. I played midweek and then not at the weekend," the 35-year-old added. "It's frustrating but my age doesn't lie.
"I have to come to terms with the fact that I can't play every game. It's hard to do because you want to play every game every week but you've got to be professional. At a club like United, when you get to 35, you have to share responsibilities.
"If you want to be successful in a number of competitions you can't just play the same team week in, week out. Now it's common for players to come in and out of the team and it seems seamless for the individual.
"I don't know [if I'll retire]. I've got to get through this season first. I hope I finish this one. Last season I said the same thing. I won't look any further than the end of the season and then re-evaluate it around that time."