I think Keane is the key here, if anyone here thinks Rafa has paid 20 million for a player (bearing in mind our chronic lack of funds) that he doesn't think we need then perhaps you don't have much faith in our manager.
I'm only trying to get into Rafa's thinking here, and from watching Gerrard in the position just behind Torres I think the answer lies with Gerrard's ability (or lack of) to recieve the ball back to goal around a congested defence/midfield. Now against the smaller teams this seems to work fine with Gerrard able to get the ball in plenty of space, turn and look for Torres' runs, and I don't think anyone can argue he causes absolute havoc in doing so. But in watching our games against the so called 'top' teams, I can see whenever an anchor man is deployed (or two) and especially with the quality of an essien/makalele or a hargreaves/anderson you can clearly see that Gerrard struggles to get any sort of grip on the game. I'd go as far to say that at times he can look completely anonymous.
Now as regard to Keane, I believe he's been bought specifically to eradicate this problem. I've watched Keane a lot over the last couple of years and I've remarked to my fiancee more than once how I'd love to see him in a Liverpool shirt. Keane has that ability to get the ball back to goal, spin off his marker and create space for other players. Gerrard is at his best when he has the ball when facing the goal, and whether or not Rafa has a plan for him being played in the centre with Mascherano but a bit further advanced, or as part of three attacking midfielders behind Torres I don't know, but what i do know (or think) is that Rafa has seen this 'problem' with Gerrard and gone about sorting it.
Time will tell, and as we've seen with Rafa over the years he will never fail to surprise you.