Manchester United manager Jose Mourinho said there were fears his players would suffer injuries on Young Boys's artificial pitch and questioned UEFA's willingness to accept such surfaces.
United won 3-0 in their Champions League Group H match on Wednesday and while upbeat about his team's performance the Portuguese manager took aim at the pitch.
"Now I can say, I don't understand how you can play the best club competition on artificial pitch," Mourinho said.
"You know, probably some fear injuries. I had some players after training yesterday - light training - and they were feeling ankles, back pains, sore.
"It's not easy, especially not for people who are not adapted to it. Also a little bit of a fear in the duels."
Before the game, Mourinho had urged his team to follow the example of Swiss tennis great Roger Federer and show they were capable of winning on different surfaces.
They accomplished that with a minimum of fuss.
"Job done. Not phenomenal but good enough," Mourinho said.
Captain Paul Pogba, 19-year-old debutant Diogo Dalot and his fellow fullback Luke Shaw were singled out for praise.
France World Cup winner Pogba scored two goals - a sublime keft-footed finish in the 35th minute and a calmly drilled 44th-minute penalty - and provided the assist for compatriot Anthony Martial's third.
"I felt Paul was a bit tired in the last part of the game but he was class," Mourinho told BT Sport.
"He gave the team the pace we needed at times, keeping possession and keeping control of the tempo."
Close-season signing Dalot, who missed the start of the campaign with a knee injury, and Shaw, often criticised by Mourinho last season for below-par performances, looked solid on the flanks.
"I thought Dalot was very good but I prefer to speak about both fullbacks," Mourinho said.
"Shaw played like he has done since the start of the season.
"Dalot is one of the best right backs in Europe already. He has a lifetime to play for Manchester United."
Young Boys coach Gerardo Seoane wsa magnanimous in defeat.
"Young Boys had a great start in front of a great crowd," he said.
"Then it was an unlucky situation and in the end Manchester United showed what they can do, and you have to accept that and congratulate those players for what they did tonight."