Leverkusen showed that they are still ready to defend the title this season, although in terms of ranking they are still below Bayern Munich because they had experienced a defeat when facing Leipzig, but the competition is still very long. This is a draw that feels like a victory for Leverkusen, because this is an away match which is not easy to take points from Bayern Munich's headquarters. Bayern Munich played hard to win, but Leverkusen's game was still disciplined enough to withstand every attack made by Bayern Munich apart from 1 goal that nested into their goal. Here you can see how Leverkusen is quite solid, because Bayern Munich recorded 18 attempts and only 3 of them managed to really go towards the goal.
If it's by the performance of Leverkusen against Bayern Munich, then I will not agree that they are ready to defend the title even if they didn't lose the match, they didn't perform so well that I will say they did better, they only went defensive at some point so as to get this draw because they understood that Munich came for a win and the only way to avoid them getting that is to make sure they score minimal number of goal and that was what they achieved with their defenses.
I will even give the chances to Bayern Munich much more than I would to Leverkusen as currently Bayern Munich only needs to keep winning and a few draws, they are going to stay ahead in the league even if Leverkusen try their best to do better.