Middlesbrough have turned down an amazing £15m bid to take Aiyegbeni Yakubu back to Fratton Park.

The unbelievable offer was made earlier this week and was rejected by Boro chairman Steve Gibson.

Portsmouth boss Harry Redknapp has been expected to make his move for the prolific striker at some stage during the close-season but it is the manner in which he has done so that will stun the Premiership.

But it is also Middlesbrough's determination to hold on to a player they signed for half the fee being offered that proves they mean business themselves ahead of the new campaign.

Under manager Gareth Southgate, Boro are determined to move forward and it is for that reason Gibson has warned Portsmouth Yakubu is not for sale at any price.

The Nigerian finished as the club's top scorer with 19 goals in his first season on Teesside, despite spending the latter stages behind Jimmy Floyd Hasselbaink and Mark Viduka in the pecking order.

That return highlighted his eye for goal and illustrated why new England boss Steve McClaren was so keen to recruit Yakubu during his time in charge at the Riverside Stadium.

Before his big-money switch to Middlesbrough a year ago, the 23-year-old made a massive impact during his first two campaigns in the Premiership.

Only Thierry Henry scored more league goals than Yakubu and it is for that reason Redknapp is so keen to land him again.

Redknapp, who had left the south-coast club before the sale of the forward was sanctioned, is desperate to find a new forward before next weekend and Yakubu is his top target.

But Middlesbrough's reluctance to accept such an offer means Redknapp could be forced to switch targets, with most alternatives available at a considerably lower price.

It has even been suggested that if they fail to agree a deal for Yakubu then Pompey will knock on the door of the Riverside Stadium again for Mark Viduka.

Southgate, whose side are still smarting from losing all four of their friendlies in Holland and Germany, knows he has to try to keep his squad together before starting the Premiership season at Reading next Saturday.

Instead of looking to sell off some of his prize assets - Tottenham are also preparing another multi-million pound bid for left-winger Stewart Downing - he is looking to strengthen.

A £4.5m bid is in the offing for Wigan right-back Pascal Chimbonda and Southgate is thought to be the favourite to land the Frenchman.

Tottenham are ready to pull out of the race to sign the defender after failing to meet Wigan's asking price and Middlesbrough are poised to step in.

There is still a chance Southgate could also return for Manchester City centre-back Sylvain Distin, while negotiations continue for Chelsea's Robert Huth.

If either Yakubu or Viduka were to be offloaded before the closure of the transfer window on August 31, Southgate will be forced to search for a new striker.

Hasselbaink's departure on a free transfer has left them with just four strikers with a real chance of starting this season, though whether Malcolm Christie can come good after nearly two years out through injury and Massimo Maccarone can finally find his feet in English football remains to be seen.

l Mark Gonzalez scored the winner on his debut for Liverpool just three minutes after coming in the Champions League qualifier against Maccabi Haifa. Haifa took the lead in the first half but Craig Bellamy equalised soon after.