Heinz has been ruled out of the clash due to a leg soft tissue injury, so Eddie Jones has called up uncapped Northampton Saints pivot Mitchell to provide cover.
Jones also has experienced scrum-halves Ben Youngs and Dan Robson in his squad for the showdown in Rome.
England go into the match knowing a bonus-point victory could see it crowned champion, depending on the outcome of the huge final-day battle between France and leaders Ireland in Paris.
The Red Rose have won all 26 matches against Italy in the tournament, scoring at least four tries - which they need for a bonus-point win - in their last six meetings with the Azzurri.
Defence coach John Mitchell wants to see England set the tone in the opening stages of what will be their first match since the tournament was halted in March due to the coronavirus pandemic.
He said: "Firstly, our goal is to win this Six Nations. We'll need to set the tone right at the start and we'll also need to be at our best.
"If we keep that focus and maintain that intent and are very good, then we'll give ourselves a very good opportunity.
"It's an opportunity for us to put smiles on faces during a really tough time in the country – that might sound generic because you might be hearing that from all sportsmen but that time has arrived for us, and that’s really important to us."
Meanwhile, flanker Tom Curry says the competition for places in the squad is pushing him to take his game to another level.
He said: "In life there is stuff that you can't effect whatsoever. Obviously as rugby players you want to be playing, but sometimes that’s not the case and especially at this time.
"I think the brilliant things about this situation is how adaptable you can be and how you can still look to get better. I think from a personal point, I feel in a really good place."