Di Maria joined United from Real Madrid last summer for a British transfer record ??59.7m and got off to a dream start with three goals and three assists in his first five Premier League games.
A wonderful chipped goal in the 5-3 defeat marked the high point of his early-season form but he struggled as the season wore on.
The 27-year-old earned a costly red card in United???s FA Cup defeat to Arsenal and failed to crack the starting line-up for seven consecutive league games upon his return, before starting the final game of the season against Hull City.
Rojo admitted Di Maria endured some struggles in his debut season at Old Trafford but is adamant his compatriot will show United fans this season why he arrived at the club with the reputation of one of the world???s best players.
“For me, the player with the most talent at Manchester United is Angel,” Rojo told the official Copa America website.
“There are great players at the club but Angel, for me, is one of the best in the team and in the world. It has been a difficult year for him. He had some problems adapting but that???s normal.
“Any player coming to a new country and a new league has to adapt to the differences and that???s what happens. But I’m sure he will do really well in the months ahead.”
Both players are currently competing in the Copa America for Argentina and will line out for La Albiceleste when they take on Paraguay on Tuesday night for a place in the final against tournament hosts Chile.