Reclaiming Manchester United's status as a dominant force in English football is not going to be easy for Jose Mourinho, says Radomir Antic.
Since the retirement of Alex Ferguson in 2013, United have struggled to hit the heights they enjoyed under the Scot, with David Moyes and Louis van Gaal both struggling during their time at the helm.
Mourinho is the latest to try and emulate Ferguson's success at Old Trafford but United have only shown glimmers of a potential recovery so far this season.
Former Real Madrid and Barcelona boss Antic believes turning United - who are already nine points behind Premier League leaders Chelsea - back into title contenders is not an easy task.
"He [Mourinho] has taken over Manchester United after Van Gaal, who didn't exactly make the team shine, so it's difficult for him," Antic told Omnisport.
"He's got the enormous task of finally substituting Sir Alex Ferguson who was a mythical figure and made Manchester United into much more than just a football club."
Meanwhile, across Manchester, Pep Guardiola's tenure at the Etihad Stadium has fared considerably better after the opening 12 games of the season, with City sitting just one point off top spot.
Antic is a big fan of Guardiola's style but stressed it will take time for the former Barcelona and Bayern Munich boss to implement it fully.
"Obviously, we need to give Guardiola some time to judge his performance. How can I put this ... we need more days," he added.