Luis Diaz will be able to feature for Liverpool in the Champions League knockout stages following his January move.
The Colombian moved from Porto in a deal that could rise to £50m.
Diaz played for the Portuguese side during the group stages but will be allowed to represent the Reds.
In previous years the winger would have been cup-tied, but UEFA changed the rules so that players who had appeared in the group stage for one club would be eligible for a different club in the knockout stages.
Liverpool will also have to fit Diaz into their 25-man squad, which has been made simple by the departure of Nat Phillips.
The centre-half, who has barely featured this term, moved to Bournemouth on loan on deadline day, thus freeing up a spot in the squad.
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Having progressed in to the last 16 Liverpool are allowed to register up to three new players in their squad and Diaz will almost certainly be included.
The Reds are still being limited to naming a 24-man squad rather than the maximum 25-man squad due to UEFA’s homegrown rules.
That is due to Harvey Elliott's inclusion, with the 18-year-old having to be registered to play in Europe despite the fact he counts as an Under-21s player.
Jurgen Klopp's side face Inter Milan with the first-leg taking place at the San Siro on February 16.
The Reds are still fighting on all four fronts so having additional options will be crucial if they are to remain in contention.
Liverpool are nine points off Manchester City in the Premier League and have a Carabao Cup final with Chelsea to come this month.
Following the signing of Diaz Klopp told Liverpool's website: “I could not be happier that we’ve been able to get this deal done and bring Luis to Liverpool.
“I have always been a believer in only signing players in January if you would want to sign them in the summer, and that’s very much the case with Luis.
“He is an outstanding player and someone we’ve been tracking for a very long time.
“We believe he has everything needed to fit into our way and adapt to the Premier League, both physically and mentally. He is a player who is hungry for success and knows you have to fight to get what you want.
"He is a fighter, no doubt. He’s a skilful team player who has always the goal in mind."
