Ronaldo, 36, left the Premier League giants 12 years ago in a then world-record move to Real Madrid sealed a sensational switch back to his former club last week from Juventus in one of the most surprising transfers of 2021.
Ronaldo, who will wear the No 7 shirt he wore with such distinction during his first stint at the club from 2003-09, will hope to have done enough to convince United manager Ole Gunnar Solskjaer he is ready to start Saturday's league game against Newcastle United.
A full house is expected at Old Trafford to welcome back a player fans continued to hold dear to their hearts despite his move to Madrid 12 years ago.
Ronaldo's first six years at the club was peppered with trophies, including three Premier League titles, one FA Cup, two League Cups and the 2008 Champions League.
He scored 118 goals during his first spell at the club, with his final goal for the club coming on May 10, 2009 with a free kick in the Manchester derby at Old Trafford.
If Ronaldo is not deemed fit enough for an immediate return this weekend, he could play his first game in the Champions League when United visit Young Boys next week.