Coutinho was heavily pursued by Barca during the summer transfer window as they desperately scoured the market for a replacement for Neymar, but the 25-year-old remained at Anfield despite submitting a transfer request and making his desire to leave Merseyside for Catalonia abundantly clear.
Coutinho has since knuckled down and delivered a number of impressive performances since returning to the Liverpool first-team, but Heskey, who spent four years at Anfield between 2000 and 2004, thinks it is matter of when, not if the former Inter Milan star joins Barcelona, who boast a four-point lead at the top of La Liga.
"I don't think Coutinho should leave Liverpool, but I think he will go to Barcelona," Heskey told Sporting Bet.
"Every player in the Premier League would have their head turned by Barcelona or Real Madrid, they're two huge clubs. When those clubs show interest, players have to entertain that move."
Despite failing to sign Coutinho in the summer, Barcelona are prepared to try and sign him in the winter transfer window, though they may have to wait until the summer before Liverpool decided to negotiate. The Brazilian may still have designs on a move to the Camp Nou but his immediate focus is fixed on Liverpool's Champions League group stage clash with Slovenian champions Maribor.
Jurgen Klopp's side have endured a rather frustrating start to life back in Europe's premier club competition and Heskey, who was part of the Reds side that won the UEFA Cup under Gerard Houllier in 2001, thinks his former side need to strike the right balance between defence and attack if they are to have any hope of success this season.
"It has been a bit of a mixed bag," Heskey said."On the one hand, Liverpool look amazing going forward and they're so exciting to watch.
"On the other hand, it's very concerning that they haven't addressed their defensive issues. This season looks like its going to be a case of 'we need to score 5 because we're going to concede 3 or 4'. The club needs to get the balance right as a priority.
Liverpool's defence has been much criticised for a number of seasons and is undoubtedly in need of surgery, but Heskey believes the Reds should look to the other end of the pitch in order to deliver a statement of intent.
The former Aston Villa and Leicester City star is keen to see Klopp's side sign Borussia Dortmund's Pierre-Emerick Aubameyang, who has been heavily linked with a move away from the Westfalenstadion in recent months. The €70m-rated Gabon international was reportedly targeted by a host of clubs during the summer but remained at Dortmund, with no interested party willing to meet their demands.
"Liverpool should sign Pierre-Emerick Aubameyang. That signing would make a real statement to both the fans and the rest of the Premier League that we mean business," said Heskey.
"Liverpool need to sign an out and out striker who will play regularly and who we can depend on to score those decisive goals. I thought Daniel Sturridge could have been that, but he struggles with injuries and Klopp doesn't pick him even when he's fit. Firmino can play up front but he's not an out and out striker and we can't expect him to fire us to the title."