Firmino and Salah each scored in the first half for Liverpool to gather all the available point and close the range in points with second place Manchester United.
Roberto Firmino put the Reds in charge as early as six minutes, assisted by Salah who doubled their lead at the 42nd minute from a brilliant Firmino assist.
As Firmino scores his 12th Premier League goal, Salah’s was the 22nd in 27 premier league games.
Southampton on the other hand forced Lloris Karius into fine saves before Salah killed them.
The win is so vital for Liverpool because of the gap it closed given the socking and at the same time expected defeat United endured given Mourinho’s poor history to win at the St. James Park.
As the Reds are now 54 points, two behind the Red Devils, Southampton descends into the danger zone of relegation.
Meanwhile former Southampton defender Virgil Van Dijk contributed to building a faultless defense system that attracted Liverpool’s interest and created reasons for his former bosses not to easily release him.
The Netherlands International maintained character and professionalism in spite of the feeling Southampton fans might have towards him as he produced an excellent performance with greater and powerful headers, vital clearances and interceptions.
Liverpool’s next fixture will be in the Champions league on Tuesday 14th February against a Portuguese side, FC Porto at the Estadio do Dragao whereas Southampton’s next fixture will be in the FA Cup at The Hawthorns Stadium as battle with Premier League’s bottom place West Brom.