Rashford scored from the spot in the 4-0 thrashing of Chelsea on the opening weekend of the season.
However, the forward could only watch on as Paul Pogba stepped up from 12 yards and missed in Monday's 1-1 draw with Wolves.
Ole Gunnar Solskjaer explained after the game that Rashford and Pogba are the team's two dedicated penalty takers.
However, the United squad want more clarity on the issue and would prefer the younger player to assume spot-kick duty whenever he is on the pitch.
Pogba has missed four of 11 attempts since the start of last season, which means he has the sixth worst conversion rate in Premier League history of those who have taken at least 10 penalties.
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