DEREK LLAMBIAS has explained a reluctance to overspend on strengthening Newcastle United's defence by insisting further expensive additions could rock the balance of the squad.

The Magpies have been caught out in recent weeks by injuries to key defenders Fabricio Coloccini and Steven Taylor, raising question marks over the clubs failure to bring in cover.

After lengthy negotiations with both Lille and Twente, Newcastle decided to pull out of deals for Mathieu Debuchy and Douglas because of transfer fees they felt had moved.

An insistence on not meeting valuations for the two players ultimately meant summer moves to St James' Park did not materialise for either.

This season's increased fixture schedule because of Europa League qualification has stretched the Newcastle squad already, but there is unlikely to be further high-profile incomings when the transfer window opens at the turn of the year.

Llambias, the club's managing director, said: "We've made it quite clear to everyone. We have 11 positions that are grade A players or Purples, as we call them. Then, under them, we have the players who come in under them to take the positions so the squad gets bigger.

"Eventually well have 33 players who will be pushing everyone. Where we are we have, in effect, 11 Purples if you count (Vurnon) Anita. He can play midfield, right-back, left-back. They are there. Centre-backs you have Colo and Steven Taylor, who are fantastic centre-backs.

"To bring in another centre-back then You have James Perch, who is doing a fantastic job, (Mike) Williamson, who is doing a fantastic job. You can't have two purples per position because the club cant afford it. You have to be realistic."

Even though Newcastle's promising financial situation is to be boosted by the £32m four-year sponsorship deal with Wonga next summer, there remains a determination to be frugal.

It is not inconceivable that one of Newcastle's Purple players would be sold at a considerable profit, which would then mean manager Alan Pardew would be on the look-out to fill that hole.

Pardew has often explained his concerns that a wealthier, Champions League club could come in and prise one or two of his big talents away if the price was right. The manager also accepts that.

But, with the transfer window closed until January 1, the Newcastle boss is keen to focus on getting his team finding top gear domestically, particularly in the Premier League.

There is a strong chance both Taylor and Coloccini, as well as goalkeeper Tim Krul, will be fully fit to face Sunderland on Sunday week.

But it has not all been good news on the injury front for the Magpies. Yesterday it was confirmed that Slovenian forward Haris Vuckic has been sidelined for six months.

Vuckic suffered knee ligament damage in the Under-21s match with Aston Villa on Monday and is awaiting corrective surgery. It is a real blow to the 20-year-old, who would have had a greater role to play in the first team picture this season.

He said: "I knew something was very wrong and I suspected that it could be cruciate ligament and the medical examination has proved that. I have to wait for surgery and then four to six months rest.

"Its very difficult mentally. I know that I will be OK. It will require a lot of time and patience. Im very sad, I was close to the first team, I was getting a chance in the Europa League."