Chelsea have started their US tour with a 4-2 defeat against a second-string New York Red Bulls side.
Victor Moses, who has been repeatedly linked with a move away from the Premier League champions in recent weeks, was given a rare start by Jose Mourinho and he threatened early on when he cut inside from the wing before testing Kyle Reynish.
New York, who fielded mostly reserves after their US Open Cup commitments earlier in the week, enjoyed their fair share of possession for much of the first half, but Chelsea continued to look the more dangerous side in attacking areas as Kurt Zouma headed wide from a Branislav Ivanovic cross.
The lead belonged to Chelsea thanks to some clever work from Oscar, who found the space to play in Loic Remy and the French striker kept his composure to slot past Reynish.
Chelsea should have extended their lead before the break, but they twice wasted good chances as Moses struck the post before Remy somehow managed to send the ball over from just a few yards out.
It was a disastrous start to a dramatic second half for Chelsea as John Terry gifted the Red Bulls an equaliser with a sloppy pass which Franklin Castellanos intercepted, and Asmir Begovic's inability to recover allowed the midfielder to tap the ball into an empty net.
Chelsea piled the pressure on after conceding the leveller, with Diego Costa heading against the bar, but it was the home fans celebrating again when 16-year-old Tyler Adams climbed highest to head home from a Castellanos cross.
It was the start of four goals in the space of seven minutes as New York extended the lead when Sean Davis powered home a fine finish after Chelsea had missed the chance to clear the danger.
Shocked into action by a New York side missing many of its key players, Chelsea pulled a goal back through Eden Hazard, who collected another inch-perfect pass from Oscar before firing past a helpless Reynish.
However, New York restored their two-goal advantage a few moments later as Davis capitalised on space in the box to find the net with a strike which Begovic may have felt he could have kept out.
A disappointing night ended with Costa missing another chance when he sprinted clear of the New York defence before shooting wide as the home side held on for the win.