Firmino scored the only goal of the game against West Brom at the weekend, while also netting the winner versus Stoke City the week before after Coutinho had previously levelled the scoring.
Both Brazil internationals have already reached double figures this term and Lovren is happy to rely on the duo to make the difference in Sadio Mane's absence due to injury.
"These two amazing guys, these two special players mean a lot for us," Lovren told the club's official website.
"Hopefully they will stay fit until the end of the season. We are missing many players, but they showed again in the second half against Stoke that they can change the game whenever they want.
"Sometimes you need that. Top teams like us sometimes depend on our big players.
"But it is not just on them, the responsibility is for everyone to do our job.
"We have a big thing to achieve: the Champions League. Everyone wants that. If you want to be a top team, you need to continue to play well in every game."
Liverpool sit third in the table with 66 points from 33 games, holding a six-point lead over fifth-placed Manchester United, although Jose Mourinho's men have two games in hand.