It is so funny to see how things doesn't last forever, look at Leverkusen who won the league unbeaten have gotten their first defeat since last season till the season by Leipzig. This shows that they might not be able to defend the title and a different club might win the league this season. If it happens so, it means that Bundesliga is becoming unpredictable.
Leverkusen has a lot of challenges this season because they will be playing in UCL which might be a distraction to them from staying focus on winning Bundesliga this season.
Last season, Bayern Leverkusen achieved a great feat after participating in the Bundesliga and winning the trophy. They also played in the Europa League and made it to the finals of the competition. The champions league they’ll be playing in this year won’t be a distraction to them but should be an encourager for them to fight for the best in this season. Getting their first defeat of the season should not make them feel bad and think that this season will not go well for them as it has for the previous season before this, they can still try and win the Bundesliga this season because they still have a lot of games to play and a lot of chances to get out of the matches they’ll play before reaching the end of the season. A defeat to Leipzig is not the end, they can still be a league contender.
Of course, experiencing defeat at the beginning of the season I think is not a serious problem, and I am sure that it will not deter the Leverkusen squad, especially Xabi Alonso, they know that the journey is still long where there are still many opportunities that they can take advantage of in the next few matches to gradually climb to the top.
I see that from the defeat experienced by Leverkusen when playing against Leipzig yesterday, quite a lot of fans are pessimistic, even though I think it can still be said to be reasonable, because of course most of the teams in the Bundesliga, especially those who were in tight competition in the top five standings last season, must have made improvements so that this season they can appear more fierce and maybe one of them is Leipzig.
The point is I am sure that this is not a big problem for Leverkusen, as you said that the beginning is not the end, and I would say that the road is still wide open for Leverkusen.