Jose Mourinho praised hat-trick hero Didier Drogba and promised Andriy Shevchenko he would not lose faith in him.
Shevchenko, however, failed to find the net once again and missed two good chances.
Mourinho said: 'He needs a goal and I can say that to stop you asking the questions. 'When he is not scoring goals he will always play in the next game.
'Until he scores a goal he is in my line-up. There is no chance to be dropped.
'If it's two, three, four or five games he will play. He will play until he scores a goal.'
Drogba became the first Chelsea player to ever score a hat-trick in the Champions League and it was his first treble for the London club.
Mourinho said: 'Three goals is always nice and it's a day to remember for him.
'But the most important thing of the day is that Chelsea go home with three points and are top of the group with six.
'Chelsea scored three and won 3-1.
'That is five or six consecutive victories for us. We are top of the league in England and top of the group in the Champions League and we are still not playing very very well.
'Didier scoring goals is not so important for me but from a personal point of view it's nice for him.'
Chelsea's main rivals in Group A, Barcelona, dropped points in Germany where they were held to a 1-1 draw by Werder Bremen. Mourinho said: 'Being top of the group is not the question. The question is six points. We have six points and we need four or five more. That's the objective now.
'We need to improve. We had some improvement last week because we have a clean week to train and we played a good game, especially from a defensive point of view.
'It was difficult at the beginning and the last part of the game was a disappointment because when you are winning 3-0 and playing with three very fast players up front you normally have the chance to score more goals.
'The performance was cool, calm and solid but we still need to work more and put the players at the top of their form.'
Levski coach Stanimir Stoilov was happy with his team who have now lost their first two games in the Champions League and conceded a total of eight goals.
Stoilov said: 'We tried everything but made some silly mistakes at the back.
'I am happy with the performance and hope that next time we will be better. We still need experience at this level.
'It has been very difficult jumping from the UEFA Cup to the Champions League and I hope our confidence will grow.'