And, Souness feels that had Rovers not got that European place then Duff would almost definately have been tempted away from Ewood Park by the lure of European football at one of the top sides.
"Damien wants to play in the Champions League, which I understand because he's a top-class player," Souness said after the comprehensive victory at White Hart Lane on Sunday.
"He'll get there one day and hopefully with us.
"We're in Europe but I feel that, if we'd done the business against the relegated teams and Bolton, we could be in a different European competition.
"We're always looking to improve. But we only took four points off West Brom, two off Bolton, one off West Ham and one off Sunderland.
"Damien's a big player and you could see what he could do today. He's a top-class player and is beginning to realise that himself.
"He signed a four-year contract last summer so has three years to run.
"And it would have to be a ridiculous offer to prize him away - and that applies to other players as well."
TOTTENHAM MATCH REPORT