The situation regarding Daniel Ayala's future is a real concern for Middlesbrough.
The defender is out of contract next summer and is yet to sign an extension to his current deal at the Riverside Stadium.
Reports from TeamTalk have suggested that the Spaniard could be the subject of January interest from Leeds United, Stoke City and Fulham as the Championship trio look to capitalise on Middlesbrough's vulnerable situation.
A move would represent the last opportunity for the Teessiders to recoup a fee for the defender, but would also leave Jonathan Woodgate's side to tackle the rest of the season without a key player.
So who could Middlesbrough look at as a potential replacement for Daniel Ayala? Let's take a look at three potential options.
Michael Ihiewkwe
Middlesbrough's new transfer strategy means that they're no longer going to pay top dollar for a defender from the Premier League.
Combine that with their current place in the Championship relegation zone, and a move to the Riverside Stadium starts to look like a fairly unattractive proposition for players.
This means that the Teessiders could look in League One, with Michael Ihiewkwe being a key option.
The 26-year-old has been outstanding for Rotherham so far this season and tops the Whoscored.com charts for being the best defender in League One for key defensive statistics.
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With Rotherham sitting in 10th in the league, it also means that the risk of joining Middlesbrough in a relegation battle is worthwhile with promotion only looking like an outside bet. A dominant force in the air, and a player who doesn't take unnecessary risks in defence, the former Wolves youngster looks to be an ideal candidate to make the step up to the Championship.
Also, the fee would likely be bang on budget for Middlesbrough's rigid new budget.
Luke Woolfenden
A similar option to Michael Ihiewkwe, but perhaps one with a more long-term aim.
The 21-year-old has made made 11 starts for League One leaders Ipswich Town so far this term, and has been hugely impressive for the Tractor Boys.
While a promotion push looks likely for the recently-relegated side, an opportunity to make that step up to the Championship would no doubt be hugely appealing for Woolfenden.
From Middlesbrough's point of view, the defender would be an affordable option who has performed consistently well at the top end of League One.
Woolfenden is still developing but being in the upward curve of his career means that he could be an ideal option to develop under Jonathan Woodgate.
Ben Gibson
We're throwing all logic out of the window with this one.
Reports from TeamTalk have suggested that Middlesbrough are considering a loan move for their former star if Daniel Ayala was to leave.
That would leave a huge hole in the team with such an experienced player moving on, and perhaps it's a situation that would call for a reliable head.
Gibson wouldn't come cheap with a loan fee and a chunk of his Premier League wages to be paid by the Teessiders, but there would be no one better to come back into the side and challenge for his hometown team as they look to stave off relegation.
The defender wouldn't fit into Middlesbrough's new transfer model, but perhaps the need for a player like Ben Gibson would be needed to replace a player and a character like Ayala.