Ander Herrera believes Ole Gunnar Solskjaer and all the Manchester United managers who have come after Sir Alex Ferguson have an almost impossible job.
United have not competed for the Premier League crown since Ferguson retired in 2013, having delivered his 13th league title with the Reds.
David Moyes, Louis van Gaal and Jose Mourinho all failed to deliver the title, with Solskjaer the latest candidate of the post-Ferguson era to try to take them back to the top.
PSG midfielder Herrera, who will line up against his former club tonight, said: “It's not easy to compare any of the managers or teams with the time that Sir Alex Ferguson was at United.
“It’s not fair with the players and not fair with managers. He's the most successful manager in Premier League history, so every comparison is not fair with the others.
“When I arrived at United, Tottenham were not one of the top six, Arsenal were struggling and not competing for trophies, now they do, and I think they're progressing as well.
“Tottenham have progressed a lot in the last few years, so now all of the other teams are prepared to fight for titles as well.
“United are the biggest club in the UK, but all the teams have improved a lot now, so you have more competitors for the titles than before.
“I think United has to not forget, because the memories are great, but this is a new situation and new era in a new Premier League.
“But they're progressing, I think. They've signed the right players and they're going to improve. I don’t think they're going backwards, I think they're going forwards.”
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