Madrid, Nov 26 (EFE).- Borussia Dortmund, last season's Champions League runner-up, dominated Napoli 3-1 on Tuesday to remain in the running for the Round of 16, while already qualified Barcelona and Chelsea posted their weakest performances of the tournament.
The German club sits in second place in Group F with 9 points, three behind Arsenal.
Napoli also has 9 points, but trails Dortmund on goal differential and must face the Gunners in the final group match on Dec. 11.
Dortmund, meanwhile, will travel to Marseille for a clash with winless Olympique.
Barça, which with 10 points is assured of a spot in the knockout phase, saw their 21-match unbeaten streak in all competitions broken by Ajax, which topped the Spanish club 2-1 despite playing down a man for most of the second half.
The outcome leaves the Dutch side with 7 points and a chance to qualify for the Round of 16 from Group H if they can beat AC Milan - who has 8 points - in Italy next month.
The Italian side smothered Celtic 3-0 at Glasgow in Tuesday's other Group H match.
Chelsea looked uninspired Tuesday in a 1-0 away loss to Basel that lifted the Swiss club into second place in Group E over Schalke 04, which managed only a scoreless tie with basement-dwelling Steaua Bucarest.
The Schalke draw guaranteed the Premier League side a spot in the Round of 16.
Perfect in its first four matches, Atletico Madrid gave up a late goal Tuesday and had to settle for a 1-1 draw with Zenit St. Petersburg.
Atletico had already clinched first place in Group G, where Zenit - with 6 points - and Porto, who have 5, are fighting for second.
The Portuguese club came from behind on Tuesday to secure a 1-1 tie with Austria Wien.