Moura, 19, has grabbed the attention of Europe's biggest clubs after establishing himself as one of Brazil's most promising young players.
The attacking midfielder has already won 11 caps for his country and Juvenico warned only an 'enormous offer' will prise him away.
Juvenico claimed a bid of £20.2million from Inter Milan had also already been declined while Real Madrid had made contact to underline the interest.
But after Chelsea's big-money offer Juvenico believes the newly-crowned European champions are leading the race for Moura.
'We did not accept the offer but of course Chelsea is the closest to signing Lucas,' he told Italian website www.fcinter1908.com.
'Inter made an offer of £20.2 million, but this was not considered sufficient by us.
'Real Madrid is one of these other interested clubs - there has been contact with the president Florentino Perez, who admires the player.
'Lucas is a big player who will triumph in Europe, but Sao Paulo will only sell him for an enormous offer.'
Asked what Chelsea's bid was, he added: '40million euros.
'I can not say right now (what price Sao Paulo would sell at) because they are assessments that are made taking into account many factors - you know the market.
'But Lucas is a fantastic player with great qualities who is giving so much to the team.'
Chelsea's position could be strengthened after they were in negotiations with Sao Paulo only last summer when they competed the signing of young striker Lucas Piazon.
Any fears the teenager would baulk at a move to Europe early in his career could also be aided by walking into a Stamford Bridge dressing room that already boasts Brazil internationals Ramires and David Luiz.
'He is still deciding where he would like his future to be but those clubs that are interested are free to do so,' Juvenico added.
'What must be decided at the end though should be decided with all relevant parties.
'He has had a great time here (at Sao Paulo) and will only leave for an important offer.'