Firmino went off injured in the draw with Manchester United last Sunday, but manager Juergen Klopp says the Brazilian has made a fast recovery and could feature at Goodison Park.
"He's been out there and running in training yesterday," Klopp said in a news conference on Friday.
"He is very positive but that is Bobby's nature. It looks really good but I don't know for tomorrow."
Sadio Mane scored twice in a more central role in the 5-0 win over Watford, a result that kept Liverpool one point ahead of champions Manchester City in the title race.
"He has been one of our best and most stable players and is performing on a really high level," Klopp said of the Senegalese. "It was nice to see a player with his quality and attitude because he really just wants to help the team.
"Hopefully it continues until May or so."
Liverpool beat Everton 1-0 at Anfield in December with a last-gasp goal by Divock Origi -- prompting a wild dash onto the pitch by Klopp that landed him a FA misconduct charge.
Victory on Sunday would mean Liverpool would have cleared another tricky hurdle as they try to land their first English league title since 1989-90, but Klopp said he will keep any celebrations under control this time.
"I'm not sure it's possible to be more motivated than we were in the previous derby," the German coach added.
"I won't celebrate like I did at Anfield again. Divock's goal was a special moment but two days before the game is not the time to look at it.
"The game was tough and it will be tough again."
Everton have not beaten Liverpool since 2010 -- losing nine and drawing nine since -- but Klopp knows they will be fired-up to put a dent in their local rivals' title charge on Sunday.
"In the game it's emotional and passionate -- that's how football should be," Klopp said. "But we need to use that loud atmosphere. The side will be really on their toes."
(Reporting by Martyn Herman; Editing by Christian Radnedge)
