Mourinho was appointed as Van Gaal’s successor at Old Trafford back in May 2016 after the Red Devils opted to part company with the former Netherlands coach.
Mourinho led Manchester United to the Europa League title and League Cup crown in his first season in charge at the club, but the Red Devils struggled in the Premier League as they ended up in sixth place in the table.
Still, their Europa League triumph meant that they secured a place in the Champions League for this season and they have successfully booked their place in the last 16.
Manchester United, however, have fallen off the pace in the race for the Premier League title this season, and their 2-1 loss to Manchester City left them 11 points behind the leaders after just 16 games of the new campaign.
And former Red Devils boss Van Gaal believes that Manchester United have not made much progress in terms of playing style under Mourinho.
Speaking to Fox Sports, Van Gaal said: “If you ask me how did I do at United, I will say it was my best year ever, given the circumstances I was working under.
“We played football that was quite alright. But it’s not football that is appreciated in England.
“And yet, right now, looking at United, I have to conclude Mourinho is not being criticised while it’s far more boring football.
“I would rather watch City play than United. You need quality in a squad and it’s clear City have a better squad.
“What United produce now is defensive football. I always played attacking football. The proof is that the opposition were always parking the bus.
“They don’t do that now because Jose Mourinho plays so defensive.”
Manchester United return to Premier League action on Wednesday night when they host Bournemouth at Old Trafford.
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