The Spanish striker has been putting in extra gym sessions on his days off to ensure he is at his best for the run-in.
“He was training yesterday - even though we had a day off - so that means he wants to improve and wants to be physically well so that is also good news for us," said the Liverpool boss.
“Fernando is not fully match fit, not really. One week ago he was not fully fit for games and he cannot be in one week - it is not a miracle.
“He has to keep working and he has spent some time in the gym and he can be better every week.
“I could say to you he is 50% and then he scores three against Wigan. He is improving but it is a question of games.
“Sometimes it is not just your match fitness, it is if you can play well or be in the right position to score the winning goal.
“Then everything changes. It is not just a physical aspect.”