Milan would've been clear at the top of the table for the first time in 16 months if they had won.
"We know that it's never easy against Napoli, but we still have another nine games to give our best," Ronaldinho told Sky Italia television.
"We've got to continue in this vein and keep our feet on the ground. We must always think positive and therefore we do.
"There's a long way to go yet and many points up for grabs, so of course we can think about the Scudetto."