Coutinho has been chased by the La Liga giants for several weeks.
However, Liverpool are determined not to sell their prized asset and have snubbed repeated bids.
But Barca keep pushing and a mega-money transfer might still be a possibility.
Messi – who is a hugely influential and revered figure at the club – is desperate for Ernesto Valverde to draft in reinforcements.
Diario Gol say Neymar has told Coutinho that there are deep-rooted issues at the club and he needs to steer clear.
Neymar also warned his pal he will be under huge pressure from Barca fans given his hefty price tag.
It’s suggested Neymar is keen to maintain cordial relations at the Nou Camp.
However, his words of wisdom to Coutinho have apparently infuriated Argentine superstar Messi.
Coutinho has played 138 games for Liverpool since signing from Inter Milan in 2013.
Barca have already spent big this summer.