Schalke will be bidding to become the first team in four weeks to retain its lead in the Bundesliga when it plays VfL Bochum on Friday.
Schalke has 26 points and replaced VfB Stuttgart last week to move two clear. Stuttgart had taken over from Werder Bremen, also on 24. In all, six teams have occupied the top spot through 13 rounds.
The lead has changed so many times because the bottom clubs have taken points off the title contenders. Bochum, in 16th place and in the relegation zone, may do the same again to Schalke.
``We have enjoyed first, but it won't be easy to keep it,'' Schalke coach Mirko Slomka said. ``Bochum is an improving team and strong in away matches.''
Slomka has to decide whether to start Lincoln now that the Brazilian playmaker is back from a torn muscle. Once considered indispensable, Schalke won three matches and drew one without him.
Bayern Munich, which is fourth with 23 points, has won twice since getting off to its worst league start in 32 years after a 1-0 loss to last-place Hannover 96.
Bayern, which hopes Mark van Bommel can continue his recent good form in midfield, plays Hamburger SV on Saturday (GOLTV, 9:30 a.m. ET) and has a score to settle.
``Unfortunately, HSV beat us twice last season _ it can't go on like that,'' Bayern coach Felix Magath said.
The 17th-place Hamburger's season has turned into a nightmare. It lost 3-1 to England's Arsenal in the UEFA Champions League on Tuesday and now has just one win from 20 games in all competitions.
Werder Bremen's recent slump had cost it the lead in the Bundesliga, but the team's confidence has been restored after beating Chelsea 1-0 in the Champions League on Wednesday.
``This match was just the latest step in a continual development,'' Bremen coach Thomas Schaaf said of beating Chelsea.
On Saturday, Bremen plays sixth-place Arminia Bielefeld (GOLTV, 11:30 a.m. ET, tape delayed), which is unbeaten in eight games.
Also, it is Hertha Berlin versus Alemannia Aachen; Hannover 96 versus Mainz 05; Eintracht Frankfurt versus Borussia Dortmund; Wolfsburg versus FC Nuremberg; Bayer Leverkusen versus Energie Cottbus; and Stuttgart versus Borussia Moenchengladbach (GOLTV, 1 p.m. ET, tape delayed).
Bayer Leverkusen is coming off of a 1-0 loss to England's Tottenham Thursday night in UEFA Cup action.
