Cologne - Remaining unbeaten with a good fifth of the season already gone is no minor achievement, and something that leading Bundesliga quartet FC Bayern München, Borussia Mönchengladbach, TSG 1899 Hoffenheim and 1. FSV Mainz 05 can clearly be proud about.

In fact, never before have four teams navigated through their first seven games without a defeat, and the chances of one of them going on to lift the revered plate are high: 31 percent of the previous 55 clubs to have made it this far without succumbing have proceeded to win the title. takes a close look at just what makes it so difficult to get the better of the aforementioned foursome...

It is not all that surprising that the defending champions, who have been beaten just three times over the past two seasons combined, have yet to leave the field defeated in 2014/15. Last year, the Bundesliga leaders made it through a stunning 28 games before losing and with (r.) and Co. having scored the most goals so far this season (15), the second most shots (124) after Borussia Dortmund (127), a league-wide best average of almost 66 per cent possession as well as the lowest number of misplaced passes in the division, Bayern München are again the dominant side in the German top flight.

Next five fixtures (home in bold): 18 October: SV Werder Bremen; 26 October: Borussia Mönchengladbach; 1 November: Borussia Dortmund; 8 November: Eintracht Frankfurt; 22 November: TSG 1899 Hoffenheim

Hoffenheim were already heading in the right direction last season, if only in terms of their attacking potential. With 72 goals scored, they would have qualified for the UEFA Champions League if that is what points were given for. In terms of goals conceded, however, they were inside the bottom three. The signings of keeper (l.) from SC Freiburg and Eintracht Braunschweig centre-back in the summer have helped strengthen the 1899ers defence, though. Only two clubs have conceded fewer so far this season, and with Markus Gisdol's men still creating the chances up front (16 clear-cut opportunities, league best), logic explains why Hoffenheim are proving so difficult to beat.

Next five fixtures (home in bold): 19 October: Hamburger SV; 25 October: SC Paderborn; 2 November: Borussia Mönchengladbach; 8 November: 1. FC Köln; 22 November: FC Bayern München

Head coach Lucien Favre has formed a strong herd of Foals in recent years, making their undefeated start to the season anything but surprising. Solid at the back with only four conceded, Gladbach have permitted only five big chances for their opponents, fewer than any other side. Their counterattack has been refined to nigh on perfection with the most shots on goal coming from breaks (15), resulting in three goals by (r.) and his team-mates. Only Bayern have a higher passing success rate (87 percent compared to 83) while only Dortmund run more on average, 122 kilometers compared to Borussia's 120.

Next five fixtures (home in bold): 18 October: Hannover 96; 26 October: FC Bayern München; 2 November: TSG 1899 Hoffenheim; 9 November: Borussia Dortmund; 22 November: Eintracht Frankfurt

Anybody around the middle of August predicting Mainz would still be unbeaten in the league two months later may have been ridiculed. Already eliminated from the UEFA Europa League and the DFB Cup, the signs were not so good for new coach Kasper Hjulmand's side, but the Bundesliga has proven to be their haven. No other team have converted as many of their big chances (80 per cent) as Mainz have, showing an uncanny efficiency in front of goal, thanks in no small part to the Bundesliga's leading scorer (l.). The 05ers have caught their opponents offside 24 times (topped only by Dortmund, 27) and come in just behind BVB and Gladbach in the running stakes with a game average of 118.5 kilometers.

Next five fixtures (home in bold): 18 October: FC Augsburg; 26 October: VfL Wolfsburg; 1 November: SV Werder Bremen; 8 November: Bayer 04 Leverkusen; 22 November: SC Freiburg