Xabi Alonso is prominent enough to handle the hurdles which will be coming his way next season. Remember he's the main reason behind the sudden peak form of Bayer Leverkusen, they're able to comprehend the situations at hand and hitting top target in each season. Bayer Leverkusen have relaxed their players and they're warming up for the big season ahead. This is not an easy one because the entailed actions involves other oppositions.
I also have no doubts about the ability of Xabi Alonso especially for this season again because from what he has shown last season at Bayer Leverkusen to be able to win the Bundesliga is something extraordinary so that it has been a good achievement for him and hopefully can be achieved again this season. However, I do not think that Bayer Leverkusen can easily face the obstacles in the UCL, because it is a competition with quite high tension and very different from any competition including the Bundesliga.
There may not be easy matches like last year in the German league because most of the teams transferred a lot of players. The league became more difficult with the transferred players. For example, Borussia Dortmund's offensive line got much stronger. Bayern Munich also got stronger with good players. Kompany also made tactical changes. Bayer Leverkusen's squad from last year may be successful this year, but it may not be.