Egypt forward Mohamed Salah made a late substitute appearance and squandered a goal-scoring chance as Chelsea claimed their first Group G win after beating Sporting 1-0 in Lisbon on Tuesday.
Salah, whose future with the Blues remains under scrutiny, replaced Eden Hazard six minutes from time and had a chance to double the team's advantage in stoppage time.
He was released by a deft through pass from Cesc Fabregas but his effort was blocked by Sporting keeper Rui Patricio.
Nemanja Matic scored the crucial first-half goal which gave Chelsea all three points.
A Fabregas free kick from the left in the 34th minute floated over the Sporting defense to the back post where Matic sent a looping header over Patricio.
The London club's slim margin of victory belied their dominance of the game, with the series of wasted chances recalling Chelsea's 1-1 home draw against Schalke in its group opener.
Worse still, Sporting came close to equalizing during a second-half resurgence.
Chelsea, the European champions in 2012, have four points. Sporting, whose young team has fewer Champions League appearances in total than Blues captain John Terry, have one point.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)