Manchester City are keeping tabs on Southampton defender and Liverpool target Virgil van Dijk and are also considering a move for Real Sociedad centre-back Inigo Martinez, who was once of interest to Barcelona.
City are currently in dreamland after setting a new Premier League record for consecutive wins (15) and have spectacularly imposed their dominance on England's top-flight, carving out an 11-point gap between them and closest rivals Manchester United.
But despite their remarkable ascent to the summit of the Premier League, coupled with their almost spotless Champions League campaign which will continue against Basel in February, City boss Guardiola is concerned by the central defensive options - or lack thereof - available to him at the Etihad Stadium and is keen to rectify the issue next month, according to the Daily Mail.
Van Dijk made no secret of his desire to leave Southampton during the summer and even submitted a transfer request in a bit force through a move to Liverpool. Jurgen Klopp's side are believed to be the Dutchman's preferred choice but Southampton are not in the mood to rush to the negotiating table with Liverpool, who apologised to the Saints for the perceived illegal approach in the summer.
Mauricio Pellegrino's men would presumably be more open to doing business with City, though they will no doubt command a fee north of £60m ($80.5m) for the Holland international, who is still on Liverpool's agenda.
Money has not been an issue for City for the last decade, but a deal for Martinez could sit better with the powers that be in Manchester if they do decide to take a frugal approach when looking to strengthen their backline. Martinez, who seemed close to joining Barcelona in the summer only for the Blaugrana to pull out late on, has a £29m release clause in his contract with Real Sociedad.
The Spaniard is highly regarded in his homeland but City may have questions over his capability to adapt to a whole new league without a full pre-season under his belt, and his lack of Champions League experience could be cause for alarm as the Citizens look to go deep into the competition.
City will have to take all those factors into account next month, but Guardiola has stressed the importance of bringing in a new central defender ahead of the business end of the campaign amid concerns of the fitness of Vincent Kompany and capability of Eliaquim Mangala.
"In that department we have few, few players and of course to handle all to competitions we are in trouble, real trouble," Guardiola said.