Liverpool may have returned to winning ways on Thursday night with a much-needed 3-1 victory away at Tottenham, but the Merseyside outfit’s evening was soured by an injury to yet another centre-back.Joel Matip was subbed off at half-time and Jurgen Klopp confirmed in his post-match press conference that the former Cameroon international’s injury was serious.Klopp revealed that Matip had sustained “ankle ligament” damage against Spurs. The 29-year-old will now undergo a scan to determine the severity of the problem, according to Goal.With Virgil van Dijk and Joe Gomez sidelined, Liverpool fans have been pleading for the club to sign another centre-back during the current transfer window, which closes on Monday.Now with Matip potentially ruled out for several weeks, the Reds have no recognised first-team central defenders in their squad.Nat Phillips came on for Matip to partner Jordan Henderson at the heart of Liverpool’s defence. Fabinho, meanwhile, missed the game in London due to a minor muscle problem.Asked if Matip’s injury will finally force Liverpool to sign a centre-back before Monday’s deadline, Klopp said: “You can imagine that we think about everything. I’m not picky but we need to find the right player.”

But who might the right player be?

List of centre-backs with expiring contracts

With time running out to make a decision, Liverpool’s board may decide to look at those centre-backs whose contracts are due to expire this summer.

A Transfermarkt list was posted to Reddit on Thursday night which shows a host of central defenders (ranked based on their current market value) with contracts that expire in 2021.

At the very top of the list is Bayern Munich’s David Alaba. The 28-year-old, who is valued at £58.5 million, has been strongly linked with a summer move to Real Madrid but could Liverpool persuade him to move to England instead?

That would obviously be some coup. Bayern surely won’t allow the Austria international to leave unless they receive a substantial offer.

Real Madrid’s Sergio Ramos is fourth on the list, although there’s zero chance of that happening for various reasons.

Alaba’s teammate Jerome Boateng might be an option, as could Wolves’ Romain Saiss.

How about Mamadou Sakho? Klopp obviously knows the Crystal Palace defender, who played at Anfield between 2013-2017, very well.

Another former Liverpool defender is Steven Caulker. The 29-year-old, valued at £3.6 million, is currently plying his trade with Alanyaspor in Turkey.

List of centre-backs available on a free

If Liverpool don’t want to fork out money on a transfer fee, though, here’s a list of centre-backs currently available on a free (via Transfermarkt).

At the top of that list is experienced Argentine centre-back Ezequiel Garay. The 34-year-old left Valencia last year and remains unattached for now.

Neven Subotic, 32, is also available after the former Serbia international left Denizlispor earlier this month. Klopp worked with the once highly-rated defender at Dortmund and might be tempted to give the defender a call this weekend.