Jurgen Klopp put Firmino on the bench but brought him on with about 20 minutes to go.
Mohamed Salah was accused of diving by Crystal Palace when he tumbled in the penalty area late in the first half at Selhurst Park.
Mohamed Salah got Liverpool up and running as they comfortably dispatched West Ham in their first Premier League fixture of the season.
Senegal and Colombia would be hoping for a Round of 16 berth from Group H.
Both Senegal and Colombia are strong contenders for a Round of 16 slot from Group H.
Senegal coach Cisse hopes that Mane can be the difference, on what promises to be a nerve-wracking final round of matches on Thursday.
FIFA World Cup 2018, Highlights, Poland vs Senegal: Senegal beat Poland 2-1 to register Africa's first victory of the tournament
Poland and Senegal will begin their campaigns in World Cup Group H.
Liverpool's Sadio Mane hopes to return to Bambali, where his family still lives, with a winners medal.
Klopp's men started their Champions League campaign in a playoff against Hoffenheim just to make the group stages back in August.
Liverpool, inspired by two-goal Egyptian Mohamed Salah, took a big step towards the Champions League final with a 5-2 win over AS Roma in their semi-final, first leg at Anfield on Tuesday.
Mohamed Salah and Sadio Mane were on the scoresheet as Liverpool ran out comfortable winners against Newcastle United.
Liverpool are third in the table, two points behind Manchester United after just one defeat in their past 19 Premier League matches.
The Senegalese forward slotted in his second as Liverpool completely outclassed their opponents, with Roberto Firmino adding his name to the scoresheet with 20 minutes to play, before Mane's searing strike completed his first European hat-trick.
The Liverpool star held off competition from Pierre-Emerick Aubameyang and Sadio Mane to take home the prize.
UEFA Champions League: Real Madrid had to wait until the 23rd minute to take the lead through Luka Modric, but a run of five goals in 15 minutes either side of half-time sent them through in style
The only previous World Cup appearance by Senegal was in 2002.
Sadio Mane was sent off after catching goalkeeper Ederson in the face during City's 5-0 win in the Premier League at Eastlands on Saturday.