The 2-1 defeat away to Benfica means Celtic must better the Portuguese club's result in the final game in Group G.
Neil Lennon's side face Spartak at Celtic Park, while Benfica travel to Barcelona.
"They're more than capable of winning [against Spartak]," said Middlesbrough forward McDonald.
"Beating Spartak in Russia was a huge result and, after that, they'll be full of confidence."
Goals by Ola John and Ezequiel Garay either side of Georgios Samaras' header put Benfica level on points with Celtic.
But the Portuguese outfit are ahead of Lennon's side on head-to-head games, and Celtic will rely on Barca avoiding a home defeat against Benfica.
McDonald said: "Celtic's home record speaks for itself and I think even a point would do for them.
"It's going to be another special night at Celtic Park. There have been quite a few in recent years and, hopefully, this is another.
"Against Barcelona there was nothing to lose, but on this occasion there's everything to lose.
"It will be interesting to see how the players react. [Victor] Wanyama being suspended and possibly Scott Brown not playing as well will be a huge loss."