Steven Caulker will spend the rest of the season on loan at Liverpool from Queens Park Rangers after the defender's previous spell at Southampton was cancelled.
Caulker, 24, was due to spend the 2015-16 season on loan at St Mary's, but the centre-back has now joined Jurgen Klopp's side until the end of the campaign.
Sources had told ESPN FC on Tuesday morning that Caulker was a surprise target as Liverpool struggle with a lengthy injury list that as of last week included all four of the senior centre-backs -- Martin Skrtel, Dejan Lovren, Mamadou Sakho and Kolo Toure.
The defender was registered before today's noon deadline so will be eligible to face Premier League leaders Arsenal at Anfield on Wednesday evening. He is due to train with Liverpool this afternoon and have a medical.
- Liverpool FC (@LFC) January 12, 2016
An official statement from Liverpool read: "The relevant paperwork has been completed in time to allow the centre-back to be eligible for selection for Wednesday evening's Premier League fixture with Arsenal at Anfield.
"Caulker, who has Premier League experience as well as being capped by England, showed a willingness to commit to the Reds at short notice.
"The 24-year-old's arrival eases the injury situation the club are currently facing in defence, which includes both short and long-term absentees."
Caulker struggled for game time at Southampton with just eight appearances for Ronald Koeman's side this term, while his most recent outing was the 6-1 home thrashing at the hands of his new club Liverpool in the Capital One Cup last month.
A statement from Championship club QPR read: "QPR defender Steven Caulker has joined Liverpool on loan.
"Caulker was due to spend the entire 2015-16 season on loan at Southampton, but that deal has been cut short so he can join Jurgen Klopp's side until the end of the campaign.
"Caulker made eight appearances in all competitions for the Saints, featuring in three Europa League fixtures for the South Coast outfit."
Caulker came through the youth ranks at Tottenham but only made 17 Premier League starts for Spurs amid loan spells in the lower leagues at Yeovil Town, Bristol City and Swansea City, playing his part in the latter club's first Premier League campaign under Brendan Rodgers' management in the 2011-12 season.
Cardiff signed him for £8 million for in 2013 and he was ever-present in their one and only Premier League campaign, scoring five goals. Last term, he missed just three league matches for QPR.
Information from ESPN FC's Liverpool correspondent Tom Bell was used in this report.