The 30-year-old head coach was appointed several months after the attacker left the Bundesliga outfit, but is aware of the impact he had at Hoffenheim and believes that the Brazilian has taken another step forward in his career since moving to Liverpool.
Firmino has become a firm favourite of the Anfield club since arriving in 2015 for €41 million.
He has scored 22 times in 40 outings this season for the Champions League quarter-finalists, adding 13 assists into the bargain, having finished last season with 12 overall.
Mohamed Salah’s explosive campaign may have eclipsed the 26-year-old this term, but that has not prevented Nagelsmann from praising his former charge.
“For me, he’s one of the top five strikers in the world,” he said.
With 13 league goals to his credit, Firmino is well on his way to setting a new personal best in this regard, having previously struck 16 for Hoffenheim in the 2013-14 Bundesliga campaign.