The Black Cats may have added two defenders over the summer by signing Sebastian Coates and Younes Kaboul, but few Sunderland fans would call them irreplaceable.
With Allardyce having a strong commitment to solid defensive play, a move to sign another centre back in January wouldn't be much of a surprise, and it would also be feasible for Allardyce to prioritise signing bigger, more physical players, having had physically dominant teams in the past.
Fitting in with that, The Sun report that Sunderland are readying a £4m offer for Sion star Leo Lacroix, after the Swiss defender impressed against Liverpool in the Europa League earlier this month.
Lacroix, 23, stands at over 6ft 5in tall, and possesses exceptional strength and aerial ability, serving as Sion's defensive giant - and his displays over in Switzerland have seemingly triggered interest in his signature.
A Swiss Under-21 international, Lacroix appears to have a bright future ahead of him, and he would certainly fit the mould of an Allardyce signing given his size and strength.
It's also stated that Leicester City and Crystal Palace are also pursuing Lacroix, with Sion allegedly resigned to losing their star defender during the January transfer window - and Allardyce is reportedly hoping to lure him to Wearside.