Mediapart and French TV program "Envoye Special" said a young black player was overlooked by PSG because of colour.
The atmosphere in the southern city of Naples is likely to be hostile, in particular for Buffon as a former Juventus player.
Mbappe found the net just four minutes after coming on, justifying his importance in an attack which has plundered 39 goals in 11 games.
As a player for Monaco, Henry appeared in 141 matches, scored 28 goals and helped the French club claim the Ligue 1 title in 1997.
The 19-year-old star of France's World Cup title run this year, Mbappe became the youngest player to score four goals in a French league match in 45 seasons.
PSG got ready for next week's Champions League opener at Liverpool with a 4-0 win over Saint-Etienne at the Parc des Princes.
Neymar scored 19 league goals and set up another 13 in only 20 games for French champion club Paris Saint-Germain.
The injury comes with less than four months until Brazil opens its World Cup campaign against Switzerland on June 17.
Edinson Cavani netted twice, and Julian Draxler, Angel Di Maria, and Neymar also scored to ensure PSG stayed 12 points clear of second-place Monaco at the top.
PSG had defender Dani Alves sent off in the 57th minute but seemed assured of securing a point until Depay decided otherwise with about 30 seconds left.
PSG, which has won the past four editions, was keen to prove a point after Strasbourg ended its unbeaten start to the season with a league win earlier this month.
Monaco, which lost 2-1 to leader Paris Saint-Germain last weekend and is already out of the Champions League, was again a shadow of the team that reached the semifinals of Europe's top competition last season.
With Neymar having a quiet game and missing a late chance, it was left to Cavani and playmaker Javier Pastore to shatter one of the league's best defences.
Draxler set up Cavani for the fourth goal and his 101st in just 144 games, with a pass from the right following a quick PSG counterattack an hour in.
Having netted a career-high 49 goals in all competitions last season, Cavani already has 11 league goals in 10 games and 15 in 13 overall.
Cavani won the foul after being knocked over by forward Bouna Sarr, and curled the ball in off the underside of the crossbar in injury time to salvage a draw.
PSG was without Edinson Cavani left out after playing for Uruguay in World Cup qualifying this week but carved out enough chances to win easily.
The 18-year-old striker started the game in a PSG attack also featuring Edinson Cavani and Brazil star Neymar, who joined this summer from Barcelona for a world record 222 million euros ($262 million).
With Paris Saint-Germain spending massively, French clubs paid out 697 million euros ($830 million) and made 619 million euros ($736 million).
Once PSG signed Neymar, the chances of Monaco holding onto Mbappe went down.
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