Jose Mourinho’s first Champions League tie since returning to Chelsea ended in disappointment as Swiss champions Basel earned a shock win at Stamford Bridge.
Oscar put Mourinho’s side ahead with an angled first-time shot into the bottom corner at the end of the first half.
Basel’s Mohamed Salah levelled when he fired across Blues keeper Petr Cech, reports the BBC.
And the home crowd was left stunned as away skipper Marco Streller won the Group E opener for the visitors with a late near-post header.
And in France, Aaron Ramsey continued his fine form to help earn Arsenal a 10th successive away win as they strode past Marseille in the Champions League.
Ramsey’s goal six minutes from time settled the contest when he collected Kieran Gibbs’ ball to fire in his sixth of the season from 16 yards.
Theo Walcott’s volley midway through the second half gained control of the game after some early scares.
A stoppage-time penalty by Marseille’s Jordan Ayew made little difference.
Ramsey brought down Andre Ayew for the spot-kick, with Marseille forward appearing to make the most of any contact.
But it did little to spoil another fine result for the Gunners, who picked up their sixth successive win since losing on the opening day of the Premier League to Aston Villa.
In some other games, Barcelona hammered Ajax 4-0, Napoli surprised last year’s runner up, Dortmund 2-1 and Milan beat Celtic 2-0.
UEFA LEAGUE RESULTS
AC Milan 2 – 0 Celtic
Chelsea1 – 2 FC Basel
Marseille 1 – 2 Arsenal
Atl Madrid 3 – 1 Zenit St P’sbg
Aust Vienna 0 – 1 Porto
Barcelona4 – 0 Ajax
Napoli 2 – 1 Bor Dortmund
Schalke 04 3 – 0 Steaua Buch’t