Mel said that he will be making changes to his team for tonight's match with Rijeka in Croatia, although he insists that he is taking the competition seriously.
"We have a lot of games and in December the Copa del Rey begins that will bring with it further fatigue and so to have all of our players available is essential," he told reporters.
"We are forced to rotate and the teams that do not are having problems, such as Real Sociedad.
"Winning tomorrow against Rijeka gives us a chance of fighting for everything and moving forward in the group. We should be enjoying this competition and the players deserve to go as far as possible in it. When we got into Europe, we knew of the cons that it would bring."
Betis drew 0-0 with Lyon in their opening group game two weeks ago.