Igor De Camargo's header for R. Standard de Liège moved them to the top of Group C and brought a swift end to FK Partizan's UEFA Cup qualification hopes.
The Brazilian forward struck in the 36th minute to make it two wins in two games for the Belgian champions, and leave their hosts without a point from three Group C fixtures. László Bölöni's side can now confirm their place in the Round of 32 with a point in their home match against UC Sampdoria next week.
Standard went for the jugular from the off in Belgrade, with Dieudonné Mbokani seeing a shot blocked and De Camargo failing to trouble Mladen Božović with a header from Steven Defour's corner. Mbokani then had another chance from a Defour corner but his weak effort trickled wide. However, the attacker atoned for that miss as his cross from the left was headed home by De Camargo.
The Serbian team made a change at the break with Adem Ljajić replaced by Marko Jovanović, and he was instantly in the thick of the action with a strike from the edge of the area that forced Rorys Aragon to make a save. Juca then fired a free-kick over the bar, and Standard defender Oguchi Onyewu made a crucial intervention to deflect away Lamine Diarra's attempt.
The hosts continued to threaten and came within a whisker of levelling just past the hour when Zoran Tošić's right-footed effort from the edge of the box hit the bar. Aragon kept out a Tošić shot from distance and denied the winger from a free-kick, and the same player later rifled the ball over the woodork. As the game became stretched late on, Božović did well to parry Defour's 20-metre drive and punch away another shot from De Camargo.