This would have been Pjanic's last season here if he stayed. We had a choice, to offer him a new long contract - because at 30 he wouldn't have accepted a short contract - or to sell him. If we kept him for one more season without offering him a new contract, we'd have lost him for free this summer. And looking at his decline, our management probably made a logical conclusion that offering him a longer contract would be a mistake.
There is no doubt in my mind that Pjanic would have been more useful than everyone else in our midfield this year. We weren't gonna win the scudetto, though, so, unless we fail to make the top 4 now, there wasn't gonna be some huge difference in our overall results. If we don't make top 4, it's gonna be costly indeed, but looking back at things, selling him was a logical choice.
Once it became clear that selling him was the way to go, it was a matter of choice and demand. Maybe we could have sold him for 25-30m euro? Maybe nobody was willing to pay that? Maybe only Barca showed interest in him and we decided it's better to make that Pjanic+12m for Arthur swap than to take some 25-30m euro for Pjanic and then search for a new midfielder. Maybe we did indeed search for another midfielder but couldn't find one for the money we had.
Imo, the main mistakes in midfield weren't made this summer. This summer was only a consequence of covid, but even more, of the mistakes that we made in the previous summer when we got Ramsey and Rabiot. In 2019 we knew that Matuidi is old, Khedira is old and broken and Pjanic will be 30 soon. We knew that in 2020 all three of Pjanic, Khedira and Matuidi will most probably be gone. We had only Bentancur left and we knew that whoever we get in 2019 was gonna be the backbone of the future midfield. We went for Ramsey and Rabiot. This is where we got it wrong. Perhaps we were forced to, after splashing all our money on Ronaldo the year before and on a potential future superstar like De Ligt. But forced to or not, it's where we fucked up. After that covid came and Arthur+McKennie weren't mistakes as much as forced decisions.