Four of United's six league wins this season have come against the Citizens, Chelsea, Leicester City and Tottenham Hotspur. The Red Devils also picked up draws against Liverpool and Arsenal but often struggle against the teams they're expected to beat.
Per Goal, Solskjaer said:
"If it's a mental thing, then we can sort it out. We'll work with the mentality of the boys.
"For me, it's been very much about margins in those games. Some freak results that we can't control. But if you look behind the results, I'm not as negative as you are. I'm not so worried, so concerned.
"If the boys are then telling me they can't get up for these games—then we've got a problem. Then I've really got to work with them because, when I played, that's how we won the league.
"We never gave points away against the lesser teams, the not-so-good teams. The Premier League is difficult —if you don't have that mentality, you won't get results."
United have surprised many by picking up back-to-back wins against Tottenham and City in the space of three days.
The latter came after they scored twice in a strong opening period at the Etihad Stadium through Marcus Rashford and Anthony Martial.
Nicolas Otamendi replied with a header late on, but the Red Devils held on for a win against their local rivals:
Football writer Kaustubh Pandey was impressed with United's performance:
Kaustubh Pandey @Kaus_Pandey17
And breathe... Probably the best Manchester United performance in recent times. It was perfect. Tactically and mentally. Every player was so good that you can't pick a man of the match out. It is time some Ole haters start trusting this process. Or start supporting Tottenham.
So too were Samuel Luckhurst of the Manchester Evening News and football writer Liam Canning, who want to see the team replicate their showing on a regular basis:
United have played 16 Premier League games this season. In the 10 of those that have not been against the division's traditional top six or Leicester—who sit in second having enjoyed a superb campaign—they've picked up just 10 points.
They also earned up a win over Chelsea in the Carabao Cup.
As a result of their difficulties in the league, they're 22 points behind leaders Liverpool and five points off the top four.
If the Red Devils are to qualify for the UEFA Champions League next season via their domestic efforts, they need to be able to perform consistently against those they should be expecting to beat.
Of those, only Newcastle are in the top half—and they'll slip to 11th if Arsenal beat West Ham United on Monday—so it's the perfect opportunity for Solskjaer's side to show if they can improve against such teams.