United were dumped out of the competition by AC Milan
Manchester United want the format of the Champions League changed to help more big clubs reach the last eight.
United lost in the first knockout stage this season, as did Real Madrid, Barcelona and holders Porto.
United chief executive David Gill said: "At the moment we effectively have a random draw after the group stage.
"Maybe we should use a system where the holders are rated number one and they play the 16th ranked team, number two versus 15, and so on."
Gill is concerned that the competition will lose some of its pulling power if the 'glamour' clubs go out early.
He added: "It's not good for the big clubs, not good for TV and sponsors if there are no Spanish clubs in the quarter-finals.
"When the draw for the group stage is made, each club's co-efficient is used.
"Given it is unlikely we will ever go back to a situation of having two group stages, maybe we should use a system during the knock-out phase that also reflects the rankings.
You can't afford to have Real Madrid and Manchester United going out in the last 16
Arsene Wenger
"AC Milan were discussing this before we played them, so it is not a knee-jerk reaction."
Arsenal manager Arsene Wenger, whose side also exited the competition at the first knockout phase, is another calling for changes.
He said: "You can't afford to have Real Madrid and Manchester United - big clubs who invest so much money - going out in the last 16.
"You will have a revolt if it continues like that.
"Seeding teams is a possibility. I don't think the formula at the moment helps the best teams.
"Maybe Uefa will use their ranking lists to influence the draw in future."
But Gill is not expecting Europe's governing body to act quickly, if they choose to act at all.
He added: "I don't think there will be any changes for next season, but it is an argument being made and I am sure Uefa will look at it."
Typical scum and ******, for once they actually got a tough drw and what do they do, moan about it as if it was unfair. I'm so gald these c*nts got knocked out!
