More than once this season, Ferguson has raised the issue of Rooney's fitness.
And even though the England man's most recent absence with tonsillitis only amounted to two games in the middle of last month, Ferguson is not intending the 27-year-old to be one of the star men who gets a rest on Wednesday.
"Wayne needs to play a lot of games to get his match-fitness up," he said.
"He's a strongly built lad and when he misses two games it takes him three games to come back.
"It's the way he's always been.
"He'll play night and hopefully that brings him on further because Saturday was his best performance of the season so far."
But Saturday's 4-3 win at Reading was far more memorable for United's abysmal defending.
As has become almost customary, they conceded the first goal. This time though, they fell behind again, even after overturning the original deficit.
It means they have now conceded 32 goals this season, their worst performance for 11 years.
Ferguson admits it is a concern ahead of Sunday's crucial trip to Manchester City.
"If we perform like that on Sunday God knows what's going to happen to us," said Ferguson.
"Saturday was like Cartoon Cavalcade and when you see City have Balotelli, Dzeko - really tall players - it's going to be a big challenge."
The potential for skipper Nemanja Vidic returning to help out should not be dismissed entirely, even though Ferguson's statement on the Serbian's readiness to play after September knee surgery were clear enough.
"I don't think Nemanja will play (tonight)," said Ferguson.
"He feels he needs another few days' training so he won't be available.
"He's not far away. He's training well now but I think another few days will bring him on better.
"But if he doesn't play tonight there's no chance he'll play in the derby game, although I wasn't considering Nemanja for Sunday anyway."