But Boro are determined to retain the services of their most valuable asset and are hoping to increase the size of Gareth Southgate's squad rather than reduce it.

Despite signing a new five-year deal, worth around £9m, in February, Downing's future continues to attract speculation, with Liverpool manager Rafael Benitez known to be an admirer.

Boro's chief executive Keith Lamb said: "We were all delighted that Stewart signed a new contract last season.

"We believe he is happy and settled here.

"Having said that, we know that Stewart has to achieve all that his talent allows, so the onus is on Middlesbrough to ensure his ambitions are fulfilled here.

"Stewart's got everything as a player and is playing possibly the best football of his career, both for Middlesbrough and for England.

"But I don't feel that he has fulfilled his potential yet. His best years are ahead of him. We believe he will become one of the best footballers in Europe."

Meanwhile, Boro are setting their sights on the Barclays Premier league's top eight and European qualification as they close in on their summer targets.

Lamb is confident manager Gareth Southgate will have two or three new faces on board by the time his players return for pre-season training on July 7.

But whatever the make-up of the squad once the new campaign gets under way, they will be looking upwards after last season's fight against relegation.

Lamb said: "We think we are capable, as a football club, of occasionally winning a cup, of finishing in the Premier League's top eight on a consistent basis and of generally giving the fans good run for their money.

"We, as a club, are certainly aiming for the top eight this season, but I know that there is the ambition and belief among the squad to achieve that too.

"That is more important than what Steve Gibson or I think because the players are the ones who can make it happen.

"We want to experience European football again, there's no doubt about that. The club, the players and the fans all want that."

Boro, UEFA Cup finalists in 2006, have spent the last few weeks working on Southgate's wish-list, and are understood to have made significant progress in their pursuit of Paris St Germain midfielder Didier Digard.

They have been linked with a series of other players as Southgate attempts to plug the gaps in his midfield, with Reading's James Harper one of those who has attracted his interest.