Lionel Messi must accept criticism at Paris Saint-Germain after supporters turned on the Argentine great, according to Michel Platini.
Platini, who has told Kylian Mbappe to follow his dreams when his contract expires at the end of the season, believes PSG have built "a great club" under their Qatari ownership.
But he questioned whether the acquisition of a string of superstar names is the best way to construct a successful team, and sympathised with Messi, who has endured a tough first campaign in Paris.
A Ligue 1 title is practically assured, but defeat to Real Madrid in the Champions League last-16 stage, from a 2-0 aggregate advantage, has stung PSG, while also delighting the club's critics.
There are critics within the ranks of the club's supporters, too, with Messi and Neymar among the players who faced loud whistling from fans at the first league game following the exit from Europe.
Former France superstar Platini knows Messi will have been affected by the whistles.
"He also understands them, but it hurts," Platini told RMC Sports. "I, too, was whistled at the Parc des Princes. But I was never whistled either at Saint-Etienne or at Juventus."
Although Platini never played for PSG, the club's home ground staged France internationals during his time as a player and coach of the national team.
"One has the right to whistle. The customer is king," Platini added. "I wouldn't do it. Everyone has the right to whistle, to insult. The football field is an outlet. Leo came to please Paris. Maybe there were other teams that wanted him. It's very hard."
Asked whether Messi made a mistake by joining PSG when Barcelona could not afford to retain him, Platini said: "He does what he wants. It is true that he is the child of Barcelona as Ronaldo was the child of Madrid. They decided to leave.
"I can put myself in their place. When I left Juve, I stopped. I was 32 years old. Barcelona and OM [Marseille] wanted me. It's complicated for a player like Leo, when you reach 34, you know you're worth a lot. But are you going to play as well as in the past?
"Lionel chose to have a new challenge. It is good for French football that he came to play in France. But he will never play as well as he did five, six years ago."
With nine rounds of games remaining, PSG lead second-placed Marseille by 12 points in Ligue 1, so silverware is coming, but the PSG of next season could be strikingly different to the current side.
Mbappe may see out his contract and leave for Real Madrid, Messi's future is beginning to look uncertain, and many would be surprised if head coach Mauricio Pochettino stays in charge.
Messi has just two Ligue 1 goals this season and seven strikes across all competitions, and Barcelona have not closed the door on the possibility of a Camp Nou comeback for their greatest ever player.
"It's hard to do better than what they did," Platini said. "They have a Messi-Neymar-Mbappe forward line. If by putting three of the best players in the world, you don't win, what should you do? Maybe have more in-depth thinking about how to play rather than taking names."
PSG continue to await Mbappe's next move. They hope he will agree to a new contract and stay, but Madrid have made their interest perfectly clear, and a fresh start at the Santiago Bernabeu holds obvious appeal.
Since arriving from Monaco as an 18-year-old in August 2017, Mbappe has scored 158 goals for PSG and added 70 assists, with his goals coming at a rate of over every 104.22 minutes. Only Robert Lewandowski (223), Messi (169) and Ronaldo (162) have scored more over the same period.
Mbappe has hit seven hat-tricks and 31 doubles, and is by far and away the leader when it comes to goals from fast breaks, netting 32 in such a manner, 15 ahead of the nearest challenger, Liverpool's Mohamed Salah.
"He must do what he dreams of, what he wants to do," Platini said.
"We have experienced 15 extraordinary years with two exceptional players who have won everything, Ronaldo and Messi. He is in pole position for the future. The future is in front of him, he can win everything. He is the player who should be the future big star for years to come.
"He is the best French player currently. He has everything to be the best, to be [winner of the] Ballon d'Or several times."