PREMIER LEAGUE new-boys Middlesbrough have completed the audacious signing of former Manchester City striker Alvaro Negredo and head coach Aitor Karanka remains on the look-out for more new recruits.

It has emerged in the last 48 hours, as revealed on The Northern Echo's website yesterday morning, that Boro’s pursuit of Serbian Neven Subotic has hit the buffers. The Borussia Dortmund defender failed a medical and requires surgery despite being keen to seal a move to the Premier League.

Middlesbrough were well down the line with a deal for the highly-rated 27-year-old, so seeing a move break down at such an advanced stage is deeply frustrating for everyone concerned.

It is a far cry from last Friday when sources close to the Teesside club were briefing that a deal was in place for Subotic to become a Middlesbrough man subject to a work permit.

The former Mainz player had been expected to travel to Marbella to meet up with the rest of the Middlesbrough squad at some stage this week provided he was granted a work permit, even if it meant having to appeal first.

Middlesbrough have not commented, but Dortmund released a statement last night.

It read: "Bad news for Neven Subotic. The investigation of a specialist in England has shown that the Borussia Dortmund player must undergo surgery in the rib area. It is expected that Subotic will be out for the rest of the year."

The centre-back’s agent Frieder Gamm had suggested earlier in the day that his player was still discussing a move to England, and strongly denied claims that thrombosis in his left arm towards the back end of last season had resulted in the deal breaking down.

Gamm said: “Neven is currently in talks with English clubs. Due to his known and already-healed thrombosis problem the medical examinations are more thorough than usual. The examinations have yet to come to a conclusion.”

Middlesbrough had identified Subotic - who was also attracting interested from Arsenal, Liverpool and Sunderland - as the ideal defensive signing to give everyone a lift at the Riverside because of his stature within the game. Reviving the deal at a later date has not completely been ruled out, although there is known to be other Premier League clubs interested in his services.

Middlesbrough have had no such problems completing the season-long loan of Negredo.

The Valencia striker has a €10m clause in the deal that could see the 30-year-old complete a move on a permanent basis next summer if all parties agree to the switch.

Negredo has already had one spell in the Premier League when he scored 23 goals in 48 appearances for Manchester City after moving from Sevilla for £16.4m three years ago.

The front-man affectionately known as ‘The Beast’ drove 400 miles from Valencia across to Marbella to join up with the Middlesbrough squad and complete the formalities of the deal.

It will be up to Karanka to decide whether he hands Negredo some match action in the remaining two friendlies of the pre-season trip to the Costa del Sol.

Middlesbrough are still to play Spanish side Alcorcon and Saudi Arabian side Al-Ahli before returning to the North-East.

Negredo was in Marbella on Tuesday night to watch the 2-1 defeat to Real Betis in Marbella and the 23-time Spanish international has joined former Valencia team-mate Antonio Barragan in the Middlesbrough ranks.

He becomes Middlesbrough’s seventh signing of the summer ahead of a first Premier League season in seven years. Karanka, who continues to be linked with Aston Villa keeper Brad Guzan despite the arrival of Victor Valdes, is still seeking more new signings.