Centre-backs are in short supply at Celtic, but the following trio - who have cost over £26 million in transfer fees between them (Transfermarkt) - could be worth a punt for Brendan Rodgers' side.
Celtic have been forced to deploy a right-back, a midfielder and a 19-year-old as emergency central defenders in recent weeks, with Erik Sviatchenko, Jozo Simunovic and Dederyck Boyata all sidelined and Kolo Toure released.
But while the Bhoys were unable to relieve their situation as the transfer window came to a conclusion on Thursday, there is still something they could do with several, potentially useful, free agents knocking about.
Here are three they might wish to consider:
Signed by Swansea City shortly after Brendan Rodgers' departure as manager, the Spaniard went on to make 75 appearances before following old boss Michael Laudrup to Lekhwiya in the Qatar Stars League. Still only 30, Chico left the Gulf nation earlier this year after picking up two league titles, and with further top flight experience in Italy as well as Spain he could fit the bill for Celtic.
Once bought for £8 million by Tottenham Hotspur, Bassong played 177 times for a variety of Premier League clubs before being let go by Norwich City at the start of the summer. The Cameroonian's old boss Harry Redknapp remains a big fan, and allowed him to train with Birmingham City recently. The Blues are well-stocked in his position, though, making a permanent transfer less likely. Should Celtic capitalise?
Despite featuring regularly in central midfield for Sunderland, Kirchhoff spent much of his early career at centre-back. At 6ft 5ins tall, the latter position is one he's certainly built for. Still only 26, and once on the books of Bayern Munich, the German could be worth a gamble by Celtic.
Which of the above would you like Celtic to sign?