In terms of regrets I still think in all of the options that Bayer Leverkusen had then Erik Ten Hag was the best candidate with the right portfolio of track winning record among the people shortlisted for that interview. So it shouldn’t be a thing for them to regret even if it didn’t work out
I think all eyes are now in Bayer Leverkusen after the departure of many key players but also because there is still interest in some of the remaining ones like Granit Xhaka from Inter Milan for example.
Now Eric Ten Hag was able to recruit few players that replaced those who went out of the team, yet some positions have only one player and depending from the strategy he will adopt, there will be difficulties in case of injuries. This problem should be taken in consideration because the upcoming season will be harder than the previous one.