Newcastle are going to be new around here after a really long break. They qualified for the Champions League in the 2003/04 season the last time. It must be times with Alan Shearer. Now they don't have one of the best squads in the EPL though. They have just consolidated the squad a little more after the sale of the team.
However this was still enough for them to make it to top 4. But to maintain this level they need to increase the squad quality more than this. Tonali has joined the team which I call a really good transfer to the area between defense and the centre of midfield. He can secure the defense area more as a solid defensive midfielder.
But there is still a need for more transfers if they aim to do some noteworthy things in the Champions League. It is important for the EPL and CL both of course.
But nobody expected them to do as well as they did in the Premier League last season and I find it a bit difficult to predict how much potential is still left to be used in the team they have and what kind of players they can sign during the transfer window that is still open for some time. I wouldn't underestimate them while at the same time not expect too much, but it is one of these teams that could be able to surprise us during the group stage. There have been underdogs in the past beating the favorites during the group stage and I wouldn't call Newcastle an underdog. They are something in between because they are not known very well yet.
I liken Newcastle's season to the one Leicester had in the 2015/16 season. It was hell of a season you know as Leicester became the EPL title winners despite not having expensive players in the team. Maybe Newcastle didn't make it to the league title like Leicester did but this was also an impressive success with an average level squad.
But indeed it is difficult to predict how more left in them to maintain it at least. Therefore this kind of teams need to strengthen their squads more to increase their chance of doing good continually. Because last season wasn't good for some top level teams like Liverpool and Chelsea in the league. Tottenham also couldn't stay in the fight for top 4.
This season could be way more competitive than before depending on the improvement of these teams.
Well I think it is hard to say whether the Newcastle United squad was average or better than that because I didn't really know any players of them. They weren't the big names hat are all over the place, but they could still be great players who were well scouted by the club and then signed.
But although I know what you mean, I think comparing the season of Newcastle to the one that Leicester City played back at the time is still not appropriate. Winning the title as Leicester City was a historic event that will never be forgotten. While I also think that the Newcastle season was great, I would not count it into the same category by far as the Leicester achievement.