It would have been a little bit easy for Erik Ten Hag to continue Xabi Alonso's legacy at Bayer Leverkusen if Bayer Leverkusen's best players didn't join other clubs this summer, but since Bayer Leverkusen's best players left this summer to join other clubs, it will be difficult for Erik Ten Hag to perform like Xabi Alonso at Bayer Leverkusen because the current squad depth of Bayer Leverkusen can't compete for the German Bundesliga title this season.
So with many Leverkusen players leaving for other clubs especially important players. And there may no longer be fierce competition in the Bundesliga if Ten Hag relies solely on the remaining players. It's a shame that Leverkusen only shone for two seasons hopefully they won't return to the dark ages.