Firmino was given his competitive debut with a 12-minute outing in Sunday's 1-0 Premier League win at Stoke - but manager Brendan Rodgers felt the 23-year-old, signed from Hoffenheim for an initial £22million with a potential £7million of add-ons, and other players short on match practice needed extra work.
Those included Liverpool's other goalscorers in a 5-1 win - Danny Ings and Lazar Markovic.
Emre Can, who also returned to Melwood later after playing in the European Under-21 Championships but played for 27 minutes at the Britannia Stadium, also featured along with Adam Bogdan, Lucas Leiva, Alberto Moreno, Divock Origi, Jordan Rossiter, Mamadou Sakho and Kolo Toure.
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