I just don't see it, the quality is missing, Pogba goes missing in the big games and Lukaku has a terrible record against top sides so yes I do think they will struggle to win against top 6. PEG won't go out there and play an attacking formation, you won't see Matic and Pogba with 3 attacking midfielders. I am confident he will play Herrera, Matic and Pogba. He will set us defensivly and look to get a goal from a set piece or pure luck, this is not a winning strategy, yes it sometimes work and they'll win games like that. Long term it is not the answer. This is why they won't challenge. It worked for Chelsea because they had one game a week and had world class Hazard, Costa in the form of his life, and no injuries to their main players. It worked for Leicester before that because they had one game a week, Vardy and Mahrez in top, top form and Kante cleaning everything up along with all other top sides just not being good enough, it was an anonamly that will probably never happen again.
Rags do not have any world class attackers, and have European football so no they won't be challenging for the title. They bought Lindelof, Matic, and Lukaku. A worse window than last year when again most pundits had them as favorites, they finished 6th, and had the easiest draw in what was the worst Europa League in years and again struggled against Celta Vigo and Anderecht, they needed ref help to beat Southampton in the league cup final and only got that far because we played our reserves against them.