"What I'll say is that we would show an interest if we thought there was any chance, but realistically I don't think he would ever come here," Ferguson told The Times.
"Yes it's true that I thought the same about Smith and probably also Ferdinand at one stage, but that's a completely different situation. I could name you 15 players who have gone between Leeds and Manchester United, but no player has gone directly between Liverpool and Manchester United in something like 40 years. It's a very different proposition."
Ferguson made no secret of his admiration for Gerrard, comparing him favourably with Keane.
"There's a lot of similarities between them, they both show that great desire and energy in their game. It's a question of how long they retain it. I think Gerrard would be the first to admit that Roy has been at that level for a long time. He has had that for more than a decade, which is incredible. Gerrard could be the pivotal player in England over the next decade - for the national team I mean, because he's certainly already that for his club."