The Portuguese head coach has spent over £300m on eight players since taking over the reins at Old Trafford back in May 2016.
Paul Pogba is Mourinho’s biggest signing after the France international returned to Manchester United in an £89m deal from Juventus.
However, the versatile midfielder has struggled to set the Premier League alight over the past 18 months or so.
Manchester United striker Zlatan Ibrahimovic scored 28 times in all competitions his debut season at Old Trafford.
The Red Devils spent £75m on Everton striker Romelu Lukaku in the 2017 summer transfer window.
The 25-year-old has scored 23 times in 43 games in all competitions in the 2017-18 season so far but has faced criticism over his record against the big teams.
Sweden international Victor Lindelof in a £30m deal from Portuguese giants Benfica in the 2017 summer transfer window.
However, Lindelof has struggled to adapt to life in the Premier League, unlike fellow centre-half Eric Bailly has impressed when fit.
But former Arsenal midfielder Nicholas believes the Red Devils players haven’t improved under Mourinho.
“Have any players improved under Mourinho?” Nicholas told Sky Sports.
“Eric Bailly and Victor Lindelof haven’t, Pogba has gone backwards, Lukaku has been okay, not breathtakingly good, but his return has been what you expect.”
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