Timo Werner pounced in first-half injury time as RB Leipzig edged the first leg of their quarter-final against Marseille.
The Germany international, who scored twice against Napoli and once against Zenit St Petersburg in the previous rounds, came up with the goods again at the Red Bull Arena.
Marseille had enough sights of goal to come away with something but lacked Werner's composure and came closest when Bouna Sarr's effort struck the crossbar.
Marseille forced the first save of the night, Peter Gulacsi up to task after visiting captain Dimitri Payet neatly picked out Kostas Mitroglou.
Leipzig continued to soak up half-chances, Morgan Sanson and Andre Anguissa both shooting off target while Konrad Laimer picked up an early booking for stopping Lucas Ocampos in his tracks.
The hosts began to exert pressure of their own, Naby Keita's powerful shot blocked by Boubacar Kamara and the lively Emile Forsberg seeing his teasing cross headed over by Ibrahima Konate.
Marseille came within a whisker of taking the lead in the 42nd minute, Sarr hitting the woodwork with a scrappy volley from Mitroglou's knockdown, only to find themselves behind at the break.
Gulacsi played his part by denying Sarr and Ocampos with a sharp double save, paving the way for an incisive counter-attack which went through Forsberg and ended with Werner drifting inside and slamming home left-footed.
The Ligue 1 outfit had two big chances early in the second half and will feel at least one should have levelled the scores.
First Ocampos failed to find a finish worthy of Anguissa's instinctive back-heel, then Payet blazed over having cut into the penalty area.
Leipzig were forced to rejig their defence when Laimer pulled up but could have extended their lead with 13 minutes left.
Werner again found himself at the sharp end, but this time his effort was blocked by Luiz Gustavo.
Leipzig full-back Lukas Klostermann ensured his side would take an advantage to France next week, reading the play impeccably in added time to snuff out a two-on-one attack from Marseille.