John Terry was dropped to the bench as Chelsea's domestic stumble was mirrored by a frustrating night in Belgium, where they were held to a 1-1 draw by Champions League Group E minnows Genk.
Chelsea hammered the same opponents 5-0 at Stamford Bridge a fortnight ago but since then have suffered losses to QPR and Arsenal, as well as a police inquiry into allegations that Terry racially abused Hoops defender Anton Ferdinand - the defender denies all charges.
Ramires converted a lofted pass from Fernando Torres to put Chelsea ahead in the 25th minute but David Luiz missed a 39th-minute penalty and the visitors were made to pay when Jelle Vossen struck a 61st-minute equaliser.
Valencia moved back into contention in the group with a 3-1 win over Bayer Leverkusen.
Second-half goals from Roberto Soldado and Adil Rami saw the Spaniards home after Leverkusen's Stefan Kiessling cancelled out a first-minute opener from Jonas, which was the second-fastest goal in Champions League history at 10.6 seconds.
Valencia's win takes them within one point of the second-placed Germans and three of leaders Chelsea, with the ailing Londoners facing a potentially crucial trip to Leverkusen later this month.
Arsenal's progression to the knockout stages will have to wait for another night after they struggled to a drab 0-0 draw with Marseille.
The north Londoners had come into the Group F encounter hoping for the victory that would see them progress to the knockout stages for the 12th successive season, although a mixture of resolute defending and poor finishing put paid to that.
Arsenal looked weary from the exertions of Saturday's 5-3 victory at Chelsea and lacked the cutting edge brought by talisman Robin van Persie, who started on the bench against the French side.
Borussia Dortmund breathed fresh life into their hopes of progressing through to the last-16 after recording a much-needed 1-0 victory over Olympiakos.
Dortmund had started the evening propping up Group F with just one point from their opening three games, but Kevin Grosskreutz's fine early goal settled the contest in their favour and earned them their first win. The triumph lifts the German champions onto four points, one above Olympiakos and three behind second-placed Marseille.
Lionel Messi scored a hat-trick as reigning champions Barcelona became the first team to book their place in the knockout stages with a 4-0 win at Viktoria Plzen.
Pep Guardiola's men proved far too strong for the Czech side, whose already tall order had become an almost insurmountable one after Marian Cisovsky was sent off for fouling Messi in the 22nd minute.
Messi tucked away the resulting penalty and added his second in first-half injury time. Cesc Fabregas netted a third on 72 minutes before Messi completed his hat-trick in the last minute to guarantee the holders' passage out of a lopsided Group H.
AC Milan joined Barcelona in the knockout stages but had to settle for a draw as they were pegged back in the second half to draw 1-1 against BATE Borisov in Minsk.
Zlatan Ibrahimovic appeared to put the Italians on their way to the win they needed with his 22nd-minute opener, but Renan Bressnan's 55th-minute penalty gave the Ukrainian side a shock point.
Gustavo Manduca's last-minute winner meant APOEL Nicosia remained unbeaten at the top of Group G after a dramatic 2-1 win over FC Porto.
Ailton Almeida scored the opening goal from the penalty spot against the run of play before Porto striker Hulk equalised in the 89th minute, also from the spot. It looked like the Portuguese side had salvaged a draw after they had dominated possession, but Manduca's 90th- minute winner sealed the win for the reigning Cypriot champions.
A goal by Nicolas Lombaerts in first-half stoppage-time guided Zenit St Petersburg to a deserved 1-0 victory over Shakhtar Donetsk as they moved a step closer to the knockout stages.
Lombaerts headed home Viktor Fayzulin's corner as the Russian side finally beat Shakhtar goalkeeper Olexandr Rybka who had been in inspired form.