Bruno Fernandes joked Fred resembled Brazilian legend Roberto Carlos after his second-half cameo at left-back during the win against Southampton.
United cruised to a win against Saints at Old Trafford, netting four first-half goals which put the result beyond doubt after Alex Jankewitz's early red card.
Ole Gunnar Solskjaer saw a chance to hand some first-team minutes to summer signing Donny van de Beek given United's superior position and rest the in-form Luke Shaw in the process.
The Dutchman was introduced alongside Anthony Martial with Fred shifting to an unfamiliar role on the left side of the back four despite Solskjaer having Alex Telles available on the bench.
Solskjaer explained that the decision to move Fred into defence was a combination of mentality and tactics as United went on to add insult to injury by scoring a further five goals.
After the game, Fernandes likened his teammate to Brazil icon Roberto Carlos but Fred rejected his suggestion with a nickname of his own.
"Go Roberto Carlos," Fernandes wrote on Fred's Instagram post to which Fred replied: "A mixture of Roberto Carlos and Marcelo," with two crying laughing emojis.
Predictably, United supporters loved the interaction and praised Solskjaer for keeping his foot on the gas after a dominant first-half.
One fan on Reddit wrote: "Imagine being 4-0 up at half-time vs a team and bringing on a forward for a defender. Ole went for jugular today. This is what Man United manager should look like."
Another wrote: "Fred and Bruno are my favourite bromance."
United are back in action at Old Trafford on Saturday against Everton.
