Bayer Leverkusen will need a perfect performance if they are to earn a result against Bundesliga title rivals Bayern Munich on Saturday, according to Xabi Alonso.

Leverkusen became the first team to go unbeaten through a Bundesliga campaign as they clinched their first title last season, ending Bayern's 11-year reign in the German top flight.

Bayern are determined to bounce back under new boss Vincent Kompany, though, and they sit three points clear of Leverkusen ahead of the teams' huge meeting at the Allianz Arena.

With four wins from four games and a goal difference of +13 (16 scored, three conceded), they have made the joint-best start to a season in Bundesliga history – only Bayern themselves in 2016-17 and Stuttgart in 1996-97 have matched that record.

Alonso is expecting a huge challenge against his former club, telling reporters: "The anticipation is great and we want to show a good game. 

"We need a perfect performance to take something home with us. FC Bayern have made a good start to the season, it will be a challenge tomorrow. 

"We need to play at our highest level, with and against the ball for 90 minutes. Bayern will go full throttle, we have to be ready for that."

Leverkusen have already conceded nine goals in the Bundesliga this term, the most they have allowed at this stage of a season since 2014-15 (also nine).

The last reigning champions to ship nine goals in their first four games of a campaign were Kaiserslautern in 1998-99, while the last holders to concede more were Bayern in 1974-75 (11).

After a rollercoaster 4-3 win over Wolfsburg last time out, Alonso is desperate to see his team tighten up at the back.

"The team has to be compact, we have to defend together as a team. We have a clear gameplan, we can't be too soft and we can't allow large gaps," Alonso said.

"We have a clear gameplan as to how we want to play. We will give everything... If we don't defend well, it's hard for the players to win. We want to be consistent. We don't want to be up and down."

Following their trip to Bayern, Leverkusen host Italian giants AC Milan in the Champions League on Tuesday.