The Red Devils, who are closing in on the Premier League title, visit Loftus Road on Saturday to try and cast Rangers further adrift at the bottom of the table - but Ferguson retains faith in his counterpart's ability.
The Scot said: "It's not easy when you're down at the bottom of the league. Harry will be the first to admit that.
"It may have helped him if he had gone a bit earlier. But with Harry's experience and ability to judge players, he will have a better chance than most in that situation."
Ferguson went on to address the financial fears of relegation, which have prompted QPR to splash out on big-name players such as France striker Loic Remy, who arrived in January in an £8m deal.
Ferguson added: "You can't make money in the Championship. You get the parachute payments, which are terrific I suppose. I don't see why it should apply itself but it is there and teams can benefit from that.
"But player contracts are an issue because some of them are on very good ones and the clubs have to pay them. If you drop down, I would imagine motivation is very difficult.
"The only place you want to be is the Premier League. That is reflected in QPR spending the money they have."
Ferguson's only task this weekend, meanwhile, is to engineer a victory that would put United 15 points ahead at the top of the standings 24 hours before closest challengers Manchester City take on Chelsea at the Etihad Stadium.
"We are going down there hoping to win. That is what our job is," said Ferguson.
"QPR are fighting for survival and we know it is going to be a hard. But that type of thing is what we need anyway. We need to keep the awareness on making sure we do our job right.
"These games have to be treated exactly as we would Real Madrid or anyone else. That is the only way we can approach them.
"But there is a brilliant spirit in the place and a good determination. With the right attitude and the right players we have a chance."