Rennes manager Julien Stephan was bewildered after Wednesday's 3-0 loss to Chelsea.
The French side copped a controversial penalty decision in the first-half, which allowed Timo Werner to give Chelsea a two goal advantage.
Brazilian defender Dalbert was ruled to have handled the ball inside the box by VAR and was subsequently sent-off with a second yellow card.
"Unless the rule has changed and we weren't aware I don't know why he decided to give handball for this," Stephan said. "When you give a second yellow for this kind of thing it kills the game. So there's misunderstanding in actual fact.
"Why do we check that and not the handball from [Kurt] Zouma? There's some misunderstanding but I don't want to go into conspiracy-theory thinking.
"It was a turning point in the game, it makes it difficult against a team like Chelsea who have good players in every position, with the numerical disadvantage.
"My players were remarkable in the last 20 minutes to put pressure and try to score a goal. I'm disappointed for them that it went the way it did."
