Injuries are part of sports and sometimes you end up with a worse result because you lose some important players but even with some injuries, they should have won the Lille game, looked very difficult for them to lose and they still lost.
Indeed, each team in football must face the injury problem. That's why a team who have busy schedule, they must have good number of players. If they have lack of players, it will be difficult to deal with injury problem.
I agree that Real Madrid should win against Lille although there were some injured players. It was unfortunate that Real Madrid as defeated by Lille. If we consider the squad quality, Real Madrid is much stronger than Lille. But Lille could play with good teamwork, so they can defeat Real Madrid. Sometimes playing football is more about the team work than the quality of the squad.
I understand injuries could be bad, but this is a team sport, not like they are playing tennis, when a tennis player is injured then they are out and can't get a result, but when a player of a team is injured they still have someone else replace him and they continue, and Real Madrid should have won this game. Right now there isn't anything they can do about it, they just need to move on and look for other games, and hope for the best to happen when the time comes, will be greater result.
Real Madrid lose may be unacceptable, but there are still some remaining matches. It is better to focus on upcoming matches than thinking too much about the lose against Lille. Sure, Real Madrid can't do anything to recover the lose. Just move on and focus on other matches.