After a traumatic week in the Champions League which saw Manchester United and Celtic defeated, Chelsea, who captured the continent's top prize last season, put in a toothless display in the Romanian capital in their last-16, first-leg tie.
The only goal of the game came in the 34th minute when Raul Rusescu beat Petr Cech from the penalty spot after he had been chopped down by Ryan Bertrand.
Chelsea manager Rafael Benitez made five changes from the side which beat West Bromwich Albion 1-0 in the Premier League at the weekend, including a recall for John Terry.
But the Londoners rarely troubled Ciprian Tatarusanu with only a late drive from Marko Marin requiring a serious save from the Steaua goalkeeper.
"It was a difficult game. It was a good result for them and the pitch was not the best," said Benitez.
"We gave away a soft penalty but we had chances. We will have to go back to Stamford Bridge next week and have confidence we can win. We all have to push together."
Newcastle, with seven Frenchmen in the line-up, carved out a 0-0 draw against Anzhi Makhachkala, ending the Russians' 100 percent home record in the tournament this season.
In a game of few opportunities, and in front of a smattering of fans inside a freezing Luzhniki Stadium in Moscow, Magpies' manager Alan Pardew won the night's tactical battle against wily Guus Hiddink.
The stalemate gave Newcastle the edge ahead of the second leg on Tyneside next week with a place in the quarter-finals at stake.
Anzhi's frustrations were perfectly summed up when 30 million-euro signing Willian limped out of the game early in the first half.
The Russians had the better opportunities to break the deadlock with Cameroon star Samuel Eto'o wasting three chances.
At the other end, playmaker Hatem Ben Arfa, returning after a three-month injury absence, and one of Newcastle's French contingent in the starting eleven, had a chip saved by Vladimir Gabulov in the Anzhi goal.
Italian title-chasers Lazio took a huge step closer to the quarter-finals with a 2-0 win in Germany against Stuttgart with Ederson and Ogenyi Onazi scoring either side of the break.
There was also an away win for Fenerbahce with Cameroon striker Pierre Webo grabbing the goal in a 1-0 win at Viktoria Plzen in the Czech Republic.