Xabi Alonso hopes to mark his 100th game in charge of Bayer Leverkusen with a victory, but the Spaniard is not underestimating bottom club Holstein Kiel. 

Alonso led his side to a win over Milan in the Champions League on Tuesday, with the Bundesliga champions one of only seven teams with a perfect record in the competition so far. 

But their fortunes in the league have been much different, taking 10 points from their opening five games, the latest of which ended in a 1-1 draw with Bayern Munich. 

Leverkusen's start to the campaign is the worst by a reigning champion in 12 years since Borussia Dortmund managed eight points after the first five games in 2012-13. 

But Alonso, who has won 67 of 99 games in charge of Die Werkself, is wary of the threat this weekend's opponents provide despite their league position. 

"Every league match is tough, and we have learned that this season already," Alonso said.

"We expect the same tomorrow. They only have a point but deserve a bit more than what they have at the moment."

"In our heads and our preparation, it is only Kiel. We have full respect. They are a good opponent, very flexible in their lineup.

"I expect to see my team to be mature and intelligent. We have to show that we are fully prepared.

"My team plays with the same motivation in every game, so I have no reason to doubt them, and we will hopefully show it tomorrow."

Many of Leverkusen's problems this term have come from defence, a part of their side that was crucial in their domestic double last season. 

Die Werkself conceded just 24 times last campaign, 15 less than Stuttgart in second place. 

Leverkusen have already conceded six goals in their last two Bundesliga games at the BayArena, as many as they let in across their previous 12 home matches combined.  

Only 1. FC Koln in 1964-65 conceded as many goals in their first two home games as champions.

And with a total of 10 goals conceded from their first five games, Leverkusen has the worst defence of a reigning champion since Wolfsburg in 2009/10 (11).

Alonso stressed the importance of improving defensively, and he is confident that a win and a clean sheet will give his side a solid foundation to build on after the international break.

"If we win then we will have had a good phase (until the international break)," Alonso said. 

"Then we can prepare for the next block of matches. It was important that we are defending a bit better than we had been last month.

"That is something we need. Without it, we are not competitive, and we want to be competitive."