The Italian goalkeeper's last European performance for the Gunners saw him produce a calamitous display in the defeat at Olympiacos last December.
But Wenger said: "He has belief and he has the mental strength to deal with that."
Wojciech Szczesny suffered an ankle injury in the 6-1 Barclays Premier League win over Southampton at the weekend, which was his first game back since a rib problem.
This means that 24-year-old Mannone, who had kept clean sheets at Stoke and Liverpool when deputising for the Poland international earlier this season, will be thrown straight into the action at Stade La Mosson.
"Vito is very close (to the Arsenal number one jersey), and he gets another opportunity now," said Wenger, who has midfielder Abou Diaby fit again following a hip problem.
With Lukasz Fabianski also sidelined because of injury, and Argentina youth international Damian Martinez not on Arsenal's Champions League squad list, 21-year-old Academy product James Shea will take an unexpected place on the bench tomorrow.
"He was on the list as goalkeeper number five at the beginning of the season and now he is number two. That shows you how quickly football can change," said Wenger.
Source: PA
Source: PA