Firmino forged a formidable understanding with Coutinho since his £29m move to Liverpool FC from Bundesliga outfit Hoffenheim in the 2015 summer transfer window.
The Reds sold Coutinho in a £142m deal to La Liga giants FC Barcelona in the January transfer window to prompt concerns about Firmino.
The South American forward has scored 15 times and has made seven assists in 36 games in the Premier League this term.
Firmino has also netted 10 times in 14 outings in the Champions League to help the Reds reach the final in Kiev.
The 26-year-old signed a new long-term contract with the Merseyside outfit to end speculation about his future.
Former Liverpool FC star Lawrenson believes Firmino has thrived in the Reds team over the past few months.
“When Coutinho left,” Lawrenson told BBC Sport.
“I thought Firmino would struggle, His mate was gone,. Maybe he would fancy a move. He has been as good as anybody since January.
“He has been outstanding. He has signed a new contract. It’s a clever bit of business.:
Liverpool FC are in fourth place in the Premier League table and need to beat Brighton and Hove Albion in their final top-flight fixture to secure a spot in the Champions League next term.
The Reds will take on current holders Real Madrid in the Champions League final in Kiev later this month.
The 18-time English champions signed Virgil van Dijk from Southampton back in January.
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