Sir Alex Ferguson believes Manchester United are yet to play their best this season despite a run of six consecutive wins, and he is relishing the prospect of finally pairing Robin van Persie and Wayne Rooney after the latter's return from injury.

The United manager confessed that he has yet to establish his best combination, with Danny Welbeck, Javier Hernández and Shinji Kagawa also in contention.

Ferguson described the Rooney-Van Persie partnership as "a terrific prospect" and said: "Probably the strongest part of the club at the moment will be in the striker department. Welbeck and Chicharito [Hernández] have been doing very well also. I could play any combination. Shinji has been terrific, he is settling in well. "

He believes Van Persie's arrival elevates competition. "It should give everyone a push," Ferguson said. "Chicharito has done nothing wrong. Danny Welbeck is promising and he has shown that with England. He is in the same position as Chicharito, they are not the first-team choices at the moment.

"That doesn't mean to say it will stay that way because competition is always healthy. At the moment I don't know where I am going in the sense of what my best partnership will be because I haven't seen Rooney and Van Persie together."

Rooney made his return in Wednesday's 2-1 win over Newcastle United in the Capital One Cup after a month's absence with a gashed leg. Like his manager, the striker welcomes a fight for a starting place. "There is a lot of competition up front but that's great for the squad," he said.

Rooney feels that following the injury his season begins now, with Tottenham Hotspur visiting Old Trafford in Saturday's late kick-off. "It does feel like the start of my season. You need that training and game time to get you to your full sharpness," he said.

Ferguson said: "It is like Van Persie at the moment, Robin has still a bit to do in terms of game time because he missed all the pre-season. Wayne has to get through that period now where he gets game time."

Since losing 1-0 at Everton in their season opener United have won six consecutive games in all competitions. But asked if his side have hit top gear Ferguson said: "I don't think so, no. The area we want to try to improve and get consistency is with the defenders. We are changing that too many times.

"When you get consistency with central defenders your results get better. That proved itself last year when [Rio] Ferdinand and [Jonny] Evans played for a long period – that was our best run of results when they were playing together all the time.

"Now we have a situation where Nemanja [Vidic] is out for two months and that leads to hopefully, if Evans and Ferdinand stay fit, they will be the partnership. In the case of Nemanja I don't think he was ever 100%. I noticed it a couple of times in training that he was limping a little bit and then he started feeling tightness in his knee.

"Obviously the main operation was to correct the cruciate but when you do cruciates there is always the danger that the cartilage or meniscus is damaged also and that was the case. He wanted to carry on and in that situation that is what tough guys can do."

Ferdinand took a knock at Liverpool though Ferguson said he is fit. "Rio got a knee in the thigh. It was a dead leg but there is no problem."

Because of the injuries to Vidic, Chris Smalling and Phil Jones, Scott Wootton will be in the squad for Spurs. The 21-year-old made his debut against Newcastle, and Ferguson said: "He will be involved tomorrow. [Antonio] Valencia is doubtful. He got a knock first of all when he went into the tackle with [Daniel] Agger and [Glen] Johnson [at Anfield], and when he got brought down he got an ankle injury. If he doesn't make tomorrow he should be OK for Tuesday [in the Champions League]."