"Then obviously the second goal gave them a lift, and then it was more hard in the second half", Benitez told BT Sport.
Manchester United are looking to win their first Premier League title since 2013 when Sir Alex Ferguson got his hands on his final top-flight crown.
"Of course (Paul) Pogba is going to be huge for them (as well)".
Mourinho's men, who had lost two of their three previous league games and had scored only twice in their last four, suddenly looked in a very awkward place.
Newcastle had threatened to cause a huge shock when they took the lead in the 14th minute through Dwight Gayle's smart finish past goalkeeper David de Gea.
That today's match against Newcastle United was Lindelöf's first Premier League start serves to underline just how disappointing the centre-back's start to life at Old Trafford has...
"But to be honest Newcastle was probably the team, not in the second-half, but in the first-half which come here and we felt a bit of instability in our defensive areas, and that was clearly not because of the defensive players but because of our balance".
The Red Devils made a brilliant start to the 2017-18 season following six victories and one stalemate in their opening seven games.
The win maintained Manchester City's eight point gap at the top of the table, but Pogba insists United have every chance of chasing down their neighbours.
"When it happened I said giving up was not an option".
However, it was mostly Manchester United from that point onwards, and goals from Anthony Martial, Chris Smalling, and Romelu Lukaku wrapped up all three points for the home side.
When the Swede opened up about his own experiences on the road to recovery, he seemed to aim another shot at Pogba's approach to getting back to fitness.
But then you play Newcastle United against Manchester United, so different levels and different teams.