The former Liverpool captain, now Rangers manager, narrowly missed out on the chance to play in the same team as the Brazil international.
Gerrard departed the Reds for LA Galaxy in the summer of 2015, a matter of weeks before the club completed a deal to bring Firmino in from Hoffenheim.
The latter has since scored 53 goals in 152 appearances for Liverpool – most recently a stunning late winner in the Champions League victory over Paris Saint-Germain at Anfield.
“Firmino is an absolute genius when you watch him close up,” Gerrard told BBC Radio 5 Live.