| Chelsea looked in good form until a penalty five minutes from time scuppered their lead [GALLO/GETTY]
Arsenal and Marseille set aside their poor league form so far this season with valuable home wins in their European Champions League group matches on Wednesday.
Arsenal edged Greek side Olympiakos 2-1 while Marseille, who have just one league win all season, pulled off an impressive 3-0 victory at home to German champions Borussia Dortmund.
Marseille top group F with six points from their two matches while Arsenal are second on four.
Elsewhere champions Barcelona eased to a 5-0 win away at BATE Borisov while AC Milan - who grabbed a last-gasp 2-2 draw with Barca in their opening group match - overcame Czech debutants Viktoria Plzen 2-0 at the San Siro.
Chelsea looked like they were on their way to making it two wins from two as they took a 1-0 lead away at Valencia, veteran midfielder Frank Lampard scoring an excellent goal on a rare start.
However, Valencia forced a deserved draw four minutes from time as Salomon Kalou was penalised for handball and Roberto Soldado made no mistake from the spot.
Arsenal made a roaring start against Olympiakos, easing into a 2-0 lead early on thanks to goals by 18-year-old Alex Oxlade-Chamberlain - the third youngest scorer for Arsenal in Champions League history - and recent Brazilian signing Andre Santos.
However, some dreadful Gunners defending allowed Olympiakos back into the match six minutes later as David Fuster made them pay.
Marseille owed their victory to Ghanaian star Andre Ayew, who scored a double, the first a fine shot from the edge of the box and the second a penalty.
Loic Remy netted in between for Didier Deschamps' side.
Barcelona had wrapped up the three points by half-time as they outclassed their Belarussian hosts.
The hosts hardly helped their cause with an own-goal to make it 1-0 and their goalkeeper Alyaksandr Gutor dropping the ball onto Lionel Messi's head for their third.
The Argentine maestro added another early in the second-half with a rasping drive to make it 14 goals in 10 matches this season.
Milan had made heavy weather of the first-half against their Czech opponents but goals by Zlatan Ibrahimovic and Antonio Cassano in the second-half gave them the breathing space they required.
Russian champions Zenit St Petersburg had earlier bounced back from their surprise opening defeat to APOEL Nicosia by beating 10-man Porto thanks to a double by Roman Shirokov.
APOEL, though, remain on top of the group as they drew 1-1 away at last season's quarter-finalists Shakhtar Doetsk.