Tottenham Hotspur suffered a surprise opening-day defeat in Group E of the 2016 UEFA Youth League on Wednesday, losing 3-2 to Monaco at the Tottenham Training Centre in Enfield.
A hat-trick by starlet Irvin Cardona was enough to give the French team the points, as Spurs battled to haul themselves back into the contest after a poor start.
Fellow group side Bayer Leverkusen beat CSKA Moscow 2-1, getting their campaign off to a strong start in Germany.
Lyon also saw success in Group H as they comfortably dispatched Dinamo Zagreb 2-0.
Real Madrid feature later in the day when they host Sporting Lisbon at the Alfredo di Stefano Stadium in the Spanish capital.