While interest in signing Alexis Sanchez from Arsenal has fallen by the wayside, Mahrez has emerged as the main contender to fill the void left by Coutinho after Liverpool reportedly began talks with the player over the weekend.
But according to former England striker Tony Cottee, Liverpool should look to improve other areas of the squad as well, with a new goalkeeper and defender need to shore-up two of Jurgen Klopp's problem positions.
The Merseysiders have shipped 28 Premier League goals this season – only Arsenal with 30 have conceded more in the top seven – while Klopp's confidence in Loris Karius and Simon Mignolet is on the wane as he continues to rotate keepers.
"Coutinho is a really big loss to the Premier League," he told Sporting Bet. "He's a quality player who will slot into that Barcelona midfield with no problem. Barcelona had the money following the sale of Neymar and flexed their financial muscle to get the man they wanted.
"It is vitally important that Liverpool reinvest that money wisely in order to qualify for the Champions League and fight for the Premier League title. They've paid over the odds for Virgil van Dijk from Southampton and he will be a huge signing, but they really do need to keep improving their defence.
"If Mahrez is available at the right price then they should snap him up but Liverpool's attack is already outstanding. It's the defence which will cost them competing for trophies when it really counts so I would prioritise a new goalkeeper and perhaps another central defender."