Mercurial defensive metronome Thomas Partey is out. I mean, it's no longer news that he's no longer an Arsenal player as he couldn't reach an agreement with the club on wages.
For me, it's sad. It has to be sad to lose such a quality player who Barcelona has been exploring ways to sign this summer. The "Octopus" is gone.
It is a done deal now that a defensive midfielder(DM) in Christian Norgaard, 31, has just been signed from Brentford to fill the Partey void.
However, looking at it holistically, especially from the club's view point, I so no cause for alarm.
Financial Angle
Norgaard is a cheaper option because frankly, he is cheaper than what Arsenal would have paid keeping Partey.
Now if we may do a little financial analysis. Working with £10m, Norgaard’s £10m transfer fee is amortised over 4 years (£2.5m per year or 50k a week) plus a salary that is likely much lower than £100k (he’s earning 40 at Brentford) which likely takes us to £125k per week (assuming 75k) which is half of what Partey was looking for being a year older than Norgaard. So it makes economic sense to bring in the Brentford man who is a Norwegian like the Arsenal’s captain– which both of them could mutually benefit from and the team at large.
Injuries
There’s a reason why Partey’s contract was not renewed last year, even earlier last season. He was playing in a way that suggested he was finished at the top level(though I knew he needed extended game time) until he started picking up gradually few games before City and finally delivered a masterclass against City to fully reestablish himself himself as the main guy, They may not trust the excellence of an over 30 player who they might feel was playing for a new contract.🤷♀️
Footballing Angle
It's another matter if you talk about the footballing side of things. Norgaard ain't Partey, so yeah the team has been weakened.
However, they have weighed the pros and cons. Undoubtedly the weakest link in that team, is the lack of a number 9, not the DM position. So really, a slightly weakened DM department, is not as big a deal as a lack of a proper striker.
Indeed if you buy a Rodri of Man City and hold on to Partey, meaning improving the DM personnel, which should potentially be an upgrade on last season, it still isn't the key signing Arsenal needs and will amount to nothing without a proper striker and even an extra winger.
I assure any Arsenal supporter that Zubimendi is used to the Arsenal style& with a full pre-season, he will hit the ground running. Noorgard knows the Arsenal way also as an opponent plus he knows the EPL( infact Arteta had the luxury of also having the fine dm of Sevlla, Aguome,23, on his list, but chose the Brentford man because he is EPL-ready). So just incase Zubimendi wobbles there's a steady head, a leader too in Norgaard, to hold-brief.
The Real Issue
My concern is a reputable striker, my concern is that Saka shouldn't be over-worked again, my concern is that Odegaard should stop letting us down, my chief concern is that Arteta should 
rotate wisely without sentiments. Luis Enrique of PSG does this so well!
Too many matches last season that Arteta left Odegaard on the pitch having a poor display when a Nwaneri was on the bench. This cost Arsenal dearly. We know how long it took Arteta to trust Lewis-Skely – it was when he had no choice. These are the real challenges!
Quite frankly the DM position is the least(or barely exists) on Arsenal’s scale of challenges.
Cheers