Substituted during Barca's win over Rayo Vallecano at the Camp Nou on Saturday, Coutinho was whistled by a small section of his own fans as he trudged off, replaced by World Cup winner Ivan Rakitic.
The Brazil playmaker has fallen behind Ousmane Dembele in the pecking order and, even with the youngster struggling for fitness ahead of their Champions League second leg against Lyon on Wednesday, Coutinho's place is not guaranteed. Lyon took a goalless draw from the opening leg.
Signed for 160 million euros ($180 million) 14 months ago, Coutinho was supposed to become one of the drivers of this Barcelona team, an indispensable part of the starting line-up, not a back-up for an unpredictable, albeit supremely talented, 21-year-old.
When Dembele sprained his ankle in January, Coutinho was given a run in the side but his performances were largely underwhelming and when Dembele recovered, the French youngster returned to the side.
"Philippe is having a good season," Gerard Pique said last weekend.
"He obviously cost a lot and that means there are higher expectations but it is what it is. You have to accept the reaction of the fans because at the end of the day they're our fans.
"We all have to give him support because we need him at his best in the final stage of the season and I'm sure he will be."
'Not for sale'
Coach Ernesto Valverde is already being asked about Coutinho's future, with a move back to England regularly touted in the Spanish press. Barcelona president Josep Maria Bartomeu has been forced to insist he is "not for sale".
In La Liga this season, Coutinho has started 16 of Barcelona's 27 matches and has come on as a substitute in nine. He has four goals and two assists, and has not completed 90 minutes since January.
The problem has been, in part, not of his own making. He arrived six months before Iniesta waved goodbye and the theory went that his craft, vision and skill made him a natural successor to one of the club's greatest ever playmakers.
But, despite trying him deeper in midfield, Valverde was unconvinced. Coutinho was pushed further forward, into the left of the front three, where his ability to cut inside and create, or shoot, seemed a better fit.
The trouble is that Lionel Messi likes to do the same from the right and, at times, the pair have seemed to be occupying the same spaces.
If Coutinho submits to Messi, the game passes him by. If he tries to match the Argentinian's output, the tendency has been to try too hard, with wild shots, complicated passes and weaving runs into busy areas of the pitch.
"We're at a club where there's an incredible demand to win," said Valverde after the win over Rayo.
"We're always hoping our players can produce something but it doesn't always happen. Sometimes things come off, sometimes they don't. But his work rate is there for everyone to see."
There is a psychological element too. Those that know him well speak of Coutinho as a shy character, one that has always made an impact through performances rather than ego or self-belief.
At Liverpool, he said he watched videos of Steven Gerrard and after arriving at Barcelona, he pledged to the do the same with Iniesta. But it would not be a surprise if Coutinho's price tag weighed heavy and the idea he could plug the gap left by Iniesta even heavier.
Valverde maintains, publicly at least, he is not concerned, but the opportunities at a club like Barcelona will not be endless. The game against Lyon is another chance.
"The thing with Philippe is he takes risks, he tries to make things happen," Valverde said last month.
"He is being watched through a magnifying glass at the moment but we have faith. We believe he'll keep moving forward."