Rooney, 28, was handed the armband at United when Dutchman Van Gaal took the reins in the close-season, however the club's fortunes have not changed dramatically after their flop under David Moyes.
Moyes led United to a seventh-placed finish in 2013-14, sacked before he served his first season out, while Van Gaal has managed just one win in five league matches plus a dispiriting 4-0 League Cup defeat to third-tier MK Dons.
"We have played well, but can improve, and I was not so satisfied with Rooney as a striker and [Juan] Mata as midfielder," Van Gaal said.
"That is why I changed. Rooney can play in more positions, he's a multi-functional player and I have tried him in a striker's position.
"He has played well, but not spectacular. Falcao is a striker and I think he can do it better."
"I'm not the player I was," Rooney said.
"But I feel I have progressed my game. I agree with the people who say my game has changed.
"I did too much running when I was younger and then didn’t have the energy to get myself into goal-scoring positions in the box.
"I'm a cleverer [sic] player now and know when to run into the box and when not to, and as a result more chances have come my way and I've scored a lot more goals for the club.
"But I am happy to play out wide. I can do a job there and I can do a job up front. It depends on the situation of each game and what the manager wants me to do.
"I don't think anyone can put a finger on my best position, but I am adaptable. I can go into midfield, drop out wide or play up-front. It just depends on where the manager wants me to play."
