Leverkusen's match with Leipzig will be tough. Leverkusen seems to be performing less than last year. So of course they can be contenders for the championship but I don't expect an undefeated championship like last year. They may probably suffer defeats this year in this race with Bayern but it is obvious that they are under great management with Xabi. It seems like it will be better this year.
It is not always easy to replicate a good and successful season. Only few teams in Europe usually does that. Going unbeaten is not an easy thing, Leverkusen managed to achieve that that last season, but it doesn't mean that they are to repeat that this season. Going unbeaten in a domestic league is an extraordinary achievement, so anyone expecting Leverkusen to repeat the unbeaten of last season this term is mistaking. At some point they are going to lose matches, but that's not going to be this weekend. Leipzig is a strong team but they are not stronger than Bayer Leverkusen at home. No matter how strong the match will be, I expect Leverkusen to win the match with a score of 2:1or even more.