Ajax sporting director Marc Overmars has dashed Barcelona's hopes of signing Matthijs de Ligt in January, saying there is no chance the defender will leave in the winter window.

Sources have told ESPN FC that De Ligt and Ajax teammate Frenkie de Jong are being monitored by the La Liga champions.

Barca failed with two bids for De Jong, who had been their primary summer target of the two, but early-season problems in defence have forced them to rethink their strategy.

El Mundo Deportivo and Diario Sport reported this week that the club would move for De Ligt, but Overmars said the player, watched by Barca's Ramon Planes as Netherlands beat Germany 3-0 on Saturday, will not go.

"The chances of De Ligt leaving Ajax in January are zero percent," he told LaRoma24.

However, he left the door open to a summer transfer, saying "it's a possibility" when asked whether the centre-back could leave at the end of the season.

De Ligt, 19, has been on Barcelona's radar for a while, but his performance in the Champions League draw at Bayern Munich, watched by sporting director Eric Abidal, accelerated their interest.

Ernesto Valverde's side have struggled at the back, conceding nine goals in their first eight league games -- the same number they conceded in their opening 20 fixtures last season.

There are also concerns over Samuel Umtiti's fitness, with the club refusing to put a timeframe on his knee injury amid reports he may need to undergo surgery that would rule him out until the New Year.

Thomas Vermaelen is due back in Barcelona on Monday for tests on a hamstring injury, with sources suggesting he could be out for up to a month.

That leaves Valverde with Gerard Pique and summer signing Clement Lenglet as his only fit centre-backs.