Chelsea defender David Luiz has put his hand up over a nasty challenge during their Europa League semifinal win over Basle.

Luiz has apologised for his tackle on Philipp Degen in the first leg of Chelsea's Europa League semi-final at Basle on Thursday.

"It was a bad tackle," said Luiz. "I knew if I had continued I could have broken the guy's leg or something like that so I took out the power. I spoke to him and said sorry because I don't like that."