Rudolph Douala`s agent says the Cameroon international has no intention of joining Middlesbrough.
Boro boss Steve McClaren has been chasing the 27-year-old even though he will not be eligible for the Uefa Cup.
But Jorge Gama said: "I can assure you that the player is not interested in moving to Boro.
"It`s nothing to do with Middlesbrough as a club, we`ve explained that the reason is because he cannot play in Uefa competitions this season."
Douala is cup-tied after playing in Sporting Lisbon`s Champions League qualifier loss to Udinese last week.
He can play either as a striker or on the wing and he caught McClaren`s eye with his performance for
Sporting Lisbon in their Uefa Cup victory over Middlesbrough last season.
"Middlesbrough is a good club with good players and a respected manager," added Gama.
"But we have been thinking seriously about this and it`s a waste of time Sporting pursuing this with Boro.
"As far as we know, there is no agreement between Sporting and Boro for the transfer.
"It`s difficult to envisage us changing our mind. We appreciate the interest of Steve McClaren. The problem is that there`s no prospect of European football."
McClaren, who has already signed striker Aiyegbeni Yakubu and left-back Emanuel Pogatetz this summer, is in the hunt for two more players.
