Barcelona boss Ernesto Valverde has suggested that the La Liga leaders will not sign a centre-back during the upcoming January transfer window unless any of his current defenders depart.

Valverde has four players to cover central defence in the form of Gerard Pique, Samuel Umtiti, Javier Mascherano and Thomas Vermaelen.

However, it has been said that Barcelona are looking to bolster the position further for the second half of the season after Valverde previously demanded in the summer that the club sign Inigo Martinez from Real Sociedad to fill the gap left by the departure of Jeremy Mathieu.

The Catalans have first refusal on a deal worth approximately €9m (£7.9m, $10.5m) to sign Yerry Mina from Palmeiras which could be activated either in January or next summer.

Last week Mina's agent and uncle issued an ultimatum to Barcelona following suggestions that Valverde was having second thoughts over bringing him in during the middle point of the season.

It has been said that the Barcelona boss would rather wait until the summer to sign the Colombian international and that the Catalans would only do so in January if Vermaelen leaves the Nou Camp.

Valverde has now confirmed those suggestions, even after he was forced to promote second-team defender David Costas to his squad to face Athletic Club Bilbao at the weekend due to the injuries suffered by Mascherano and Vermaelen.

"I think that with four centre-backs in the squad is enough. Right now we have four and Vermaelen is yet to play in La Liga. We have four players for two positions," Valverde said in a press conference ahead of the Champions League clash with Olympiacos.

"Another thing would be if one of them is not here [because someone leaves in January] but in principle we have four centre-backs and we think that we can pull forward with them [until the end of the campaign]."

Vermaelen has made just one appearance in the Copa del Rey since returning to Barcelona in the summer following an unsuccessful loan spell at AS Roma.

However, Valverde has still managed to form a solid backline with the other three centre-backs at his disposal, with the Catalans having only conceded three goals in their opening 10 La Liga games.

Those impressive stats have helped Barcelona to emerge as the main favourites to win the La Liga title as they are already four points ahead of Valencia and eight in front of Real Madrid and Atletico Madrid.

But the Barcelona boss believes that it is still too soon to make such a prediction, pointing out that Real Madrid's latest 2-1 defeat at Girona proves that they could also drop points against any team.

"It is a very difficult competition. We suffered at San Mames, Real Madrid lost at Girona, Atletico dropped points with Villarreal and Valencia won narrowly at Alaves. Every point matters," Valverde said.

"We are worried about every rival and at the same time about anyone. We have to focus on ourselves. It is still soon. These gaps are not definitive and it's still very early. The natural title rivals are Real Madrid and Atletico but you can't forget Valencia who are only four points behind us and Sevilla. It's important to worry about all of them but also to focus on ourselves."