The Red Devils come into the game in the midst of poor form, having won just two matches out of seven.
In the Champions League, Ole Gunnar Solskjaer’s men have won one and lost one.
Ronaldo has now issued a rallying cry to his team mates, as they seek to bounce back against the Serie A side.
The 36-year-old wrote on Instagram: “Our time is coming.
“We have to show what we are made of and the Champions League is the perfect competition to prove ourselves to the world.
“No excuses! Let’s go!”