Second-placed Bayern dropped nine points behind Werder with 14 games remaining.
UEFA Cup holders Sevilla, rescued by a last-gasp goal in normal time from goalkeeper Andres Palop, kept their defence alive by overcoming Shakhtar Donetsk to reach the quarter-finals on Thursday.
Two clinical finishes from Bulgaria striker Dimitar Berbatov took twice winners Tottenham Hotspur through to the UEFA Cup quarter-finals on Wednesday.
A round-up of weekend action in the main European leagues.
Bayern Munich struggled to a 1-0 win over TSV 1860 Munich four days before their Champions League showdown with Celtic.
Despite the defeat Chelsea remain top of the group with 10 points, the same as Werder and two ahead of Barcelona, in the Champions League.
Holders Barcelona must beat Levski Sofia to make sure of avoiding a shock exit from the UEFA Champions League.
A summary of Wednesday night's matches in the Champions League.
Chelsea also got their Champions League campaign off to a good start, beating Werder Bremen 2-0.
The ace midfielder has been in Germany's squad for the Euro 2004 qualifier against Scotland.
They were beaten by Werder Bremen 1-0.
Favourites Barcelona will meet Benfica in the quarter-finals of the UEFA Champions League.
Twice in arrears Rangers earned a 2-2 home draw with Villarreal
Barcelona earned a valuable 2-1 away win at Chelsea, with the home side playing most of the match with only 10 men.
A round-up of weekend action in the main European leagues.
Udinese bowed out of their first ever Champions League campaign after their 2-0 home defeat to Barcelona.
Twice former winners Benfica came from behind to beat the English side 2-1 to reach the last 16 of the tournament.\nA round-up of Wednesday's matches.
Champions Barcelona produced another sparkling display to crush Racing Santander 4-1 and reclaim top spot in the Primera Liga.
Real Madrid and Bayern Munich both had their leads cut in the Primera Liga and Bundesliga respectively after suffering away defeats.
Real Madrid extended their lead in Spain to eight points after crushing Valladolid 7-0.
Inter Milan moved eight points clear in Italy after a 1-0 win over strugglers Empoli.