The Red Devils suffered a 1-0 defeat to Wolverhampton Wanderers in the Premier League on Monday, and Luke Shaw suggested after the match that the squad were not "together".
According to The Express, Harry Maguire, Edinson Cavani and Mason Greenwood are among the players to have found Ronaldo's return 'a challenge to their expected roles', while there are also concerns over the forward's influence over Portuguese-speaking players at the club.
The report claims that the dressing room 'has grown into several small cliques', with the team struggling to come together, which was a criticism aimed at the players by former club captain Gary Neville following the 1-1 draw with Newcastle United on December 27.
Ronaldo has scored 14 times in 21 appearances for Man United since returning to the club last summer, including eight goals in 16 Premier League outings.
Rangnick's team are now preparing for back-to-back matches against Aston Villa, facing Steven Gerrard's side in the FA Cup on January 10 before tackling them in the Premier League five days later. body check tags ::