Manchester United manager Jose Mourinho had the biggest rebuilding job of any boss at the top end of the Premier League, according to Rio Ferdinand.
Mourinho spent a £89.3 million world-record fee on signing Paul Pogba and also brought in Zlatan Ibrahimovic, Henrikh Mkhitaryan and Eric Bailly over the summer -- but the club are seventh in the Premier League, five points adrift of Manchester City and Arsenal.
United have also lost a Europa League group game, having been defeated 1-0 away against Feyenoord, which has increased the pressure as they prepare to face Fenerbahce in that competition on Thursday.
When Ferdinand was asked if he thinks Mourinho has had the most work to do among the title challengers, the former United defender told BT Sport: "Yeah, I do. There was a lot to do. There was a lot of cleaning up to do.
"There was a big void in the group -- in terms of mentality to win. The personalities needed to be brought out of the players to perform. There was a lot of rebuilding of characters to be done. All of that added up, in finding out who was right and who was wrong [for United].
"He had the biggest job of the lot, out of all the other guys, although he had a lot of money to spend."
There has been some inconsistency of selection and formation at United this season, plus injury issues -- which has contributed to the likes of Pogba and Mkhitaryan failing to fire consistently so far.
Ferdinand said: "Out of the top teams in the Premier League, he's the one still trying to work his best team. I don't think, still, he is there."