Barcelona threw away a three-goal half-time lead on the day Xavi Hernandez was appointed coach.
Celta Vigo scored in the 96th minute to complete a stunning comeback in La Liga on Saturday.
Real Madrid then held off Rayo Vallecano’s revival to win 2-1 and return to the top of the table, two points clear of Real Sociedad, who face Osasuna on Sunday. Radamel Falcao gave Rayo hope late on.
“We had a lot of chances to finish the game and when they scored, we suffered,” said Ancelotti. “But I’m happy. Until their goal it was our best performance of the season.”
Another deflating result for Barca was made worse by another injury for Ansu Fati, who put his team in front and then had go off with a hamstring problem.
Goals from Sergio Busquets and Memphis Depay had Barcelona 3-0 ahead after 34 minutes at Balaidos but Celta stormed back, Iago Aspas scoring twice either side of a Nolito header to seal a 3-3 draw.
“We forgot how to play in the second half,” said Barcelona midfielder Frenkie de Jong. “We lacked personality.”
Aspas’ equaliser, with a brilliant shot from the edge of the area, came with 95 minutes and 34 seconds on the clock and left the Barcelona players crumpled on the floor.
It is now Xavi’s job to pick them up, with the team’s new coach watching from Barcelona, where he had landed around three hours before kick-off.
