Celtic boss Ronny Deila has told the Scottish Sun that Dundee United have little option but to listen to their offers for their best players.
His description of them as a 'small club' however is likely to further enrage United fans, who have already seen Celtic snap up Stuart Armstrong and Gary Mackay-Steven this season.
The same paper this week claimed Celtic were interested in striker Nadir Ciftci and youngster John Souttar.
Deila said: "It’s always tough for smaller clubs to lose players.
"Small clubs need to do that more than the bigger clubs. But we also do the same so every club has this decision to make.
"I can understand they’re upset, but, again, they have to see it as a big, big honour that they’re producing players that others want."
Celtic piled on further pain on Dundee United this season, beating them in the Scottish League Cup Final, and the Scottish Cup quarter-final.
Armstrong's move in particular to Celtic will have left him feeling he made the right decision, scoring against Inter Milan in the Europa League, while both he and Gary Mackay-Steven appear destined to end the season with title winner's medals.
Celtic have won eight of their last 10 games and are eight points clear in first place, while Dundee United have won only one of their last 10, and have slipped to fifth place.