The 18 year-old Brazilian scored inside the final 10 minutes to ensure Chelsea would share the friendly spoils with the French side.
The promising Brazilian midfielder netted on 81 minutes to cancel out Nene's first-half opener as Roberto Di Matteo's men finished strongly after a largely uninspiring performance.
For PSG boss Carlo Ancelotti the late setback marred an otherwise impressive performance from his new team against his former club - one which promises much for the coming Ligue 1 season after a sensational summer of spending in the transfer market.
Eden Hazard kept his place in the Blues starting lineup after a virtuoso debut display against the Seattle Sounders, while youngsters Sam Hutchinson, Kevin De Bruyne, Gael Kakuta and Romelu Lukaku were also given the opportunity to impress.
PSG boss Ancelotti was unable to call upon either Zlatan Ibrahimovic – set to join up with his new teammates on Tuesday – or Thiago Silva, who is away with Brazil’s Olympic football squad, but nevertheless fielded a strong XI which boasted another big-money summer signing, former Napoli star Ezequiel Lavezzi.
And the tricky Argentine spurned a glorious chance to open the scoring in the third minute, ghosting between the statuesque duo of Hutchinson and Cahill before firing tamely against the legs of the sprawling Petr Cech from point-blank range.
Just five minutes later he was in the thick of the action again, racing beyond the Chelsea backline and touching the ball past the onrushing Cech before going to ground, only to be booked for diving.
Much of PSG’s early success had come against the youthful pairing of Hutchinson and Kakuta on Chelsea’s right flank, so it was no surprise when, on, 30 minutes, it yielded the opening goal.
A neat and incisive midfield interchange sent Javier Pastore cantering into the area and, after bamboozling both Kakuta and Cahill, his shot crashed against the post, only for Nene to follow up and slot the ball home, despite the best efforts of David Luiz on the line.
The Chelsea response was slow and underwhelming, with captain Frank Lampard’s speculative 35-yard free-kick four minutes from halftime yielding its first shot on target. Douchez gathered it easily, and PSG deservedly carried its lead into the break.
Both sides made numerous changes of personnel at the interval, but it was the Blues who showed greater improvement in the second half, as the introduction of Ramires and Marko Marin on the flanks injected some much-needed urgency both in and out of possession.
Despite this, however, Di Matteo’s men still struggled to create anything of substance when faced with organized and disciplined PSG defending. Hazard’s mis-hit corner on 57 minutes somehow found its way through to Branislav Ivanovic, who sliced wide under pressure.
A further raft of Chelsea changes followed on the hour mark in a bid to reverse its fortunes, including the introduction of John Terry, making his first appearance of pre-season, as well as youngsters Piazon, Nathanial Chalobah and Josh McEachran.
But it was PSG which continued to show greater incisiveness, and substitute Guillaume Hoarau wasted a guilt-edged opportunity to double the lead when he latched onto a pinpoint lofted pass from Pastore and headed wide from a unmarked position.
Chelsea looked condemned to defeat, but it finally broke through nine minutes from time when Piazon exchanged passes with countryman Ramires while driving into the penalty area before side-footing the ball past a helpless Douchez to secure his side a share of the spoils.
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