The forward picked up an ankle injury during PSG's 1-0 victory over Saint-Etienne in the Coupe de France final last week and was later seen leaving the Stade de France on crutches, which sparked speculation as to whether the 21-year-old would play again this campaign.
The Frenchman missed PSG's Coupe de la Ligue final victory over Lyon last Friday and, despite manager Thomas Tuchel expressing doubt over Mbappe's fitness, Herrera believes that the forward could be fit in time for their Champions League last-eight match.
"We are optimistic with Kylian. We have seen that he can walk," Herrera told the Daily Mail.
"He's very professional, he's young. He really wants to play and we can be very calm. He works every day, morning and afternoon.
"But if it's not possible for him to play, we also have other solutions. Kylian is very important and I'm sure he will try to play."
PSG are hoping to win their first ever Champions League title this month in what will be a World Cup-style tournament held in Lisbon.