Barcelona fell to a 2-1 defeat at Monaco on Thursday in their Champions League opener, hindered by an early red card shown to Eric Garcia.
Hansi Flick’s side have started the season with a perfect record after five La Liga matches but struggled to find their best level against the Ligue 1 side.
After Garcia was sent off for pulling down Takumi Minamino as he ran through, Maghnes Akliouche fired Monaco ahead.
Five-time winners Barcelona, last crowned European champions in 2015, have struggled in Europe in recent seasons, particularly away from home and were brought crashing down to earth in the French Riviera.
Monaco thrashed Barcelona in a pre-season friendly and had the Catalan giants’ number for much of the clash at the Stade Louis II.
A careless pass from Barcelona goalkeeper Marc-Andre ter Stegen put Garcia under immediate pressure and he tangled with the Japan international as he tried to stop him running in on goal.
“We didn’t understand each other well in that situation and I feel bad for Eric, as in the end it hurts him and we had to play nearly 80 minutes with one less player,” Ter Stegen told Movistar.
“Something happened that shouldn’t have, to anyone, to me or to him… this defeat hurts because with 10 men we still showed up and tried to take at least a point.”
Monaco soon took the lead after 17 minutes when Akliouche worked his way into the box and finished well under little pressure.
With Barcelona at a numerical disadvantage the hosts were on top and Raphinha squandered the visitors’ best openings despite his impressive domestic form of late.