Coming on top of the weekend victory at Hoffenheim, the result is another big step on the road to recovery for Bruno Labbadia's troops, who had previously been stuck in a dangerous downward form spiral.
Chances for VfB
After some early sparring VfB almost went in front in the eighth minute, Serdar Tasci thundering a header inches over the bar from the visitors' first corner of the match. Genk pressed forward in response, but they were almost caught out on the quarter-hour when keeper Laszlo Köteles made a goalline clearance from Shinji Okazaki's lob after having punched a Vedad Ibisevic header down into the path of the Japanese forward.
The home side continued to look the more impressive in terms of their short-passing game but once again it was Stuttgart who came close just shy of the half-hour mark when Ibisevic cut the ball back for Martin Harnik to hammer narrowly over.
Boka with the breakthrough
As the half progressed, Genk were sitting ever-deeper and awaiting their own opportunities on the break, but with the interval fast approaching, it was their Bundesliga guests who broke the deadlock.
Boka latched onto the ball on the edge of the box following a corner and the full back's shot took a double deflection off Genk duo Khaleem Hyland and Anele Ngcongca on its way past Köteles into the net.
Game effectively over
The second half started to a similar pattern, with Stuttgart carving out a couple of further half-chances against their Belgian hosts. Thirteen minutes in, William Kvist freed up Gentner with a through ball and the midfielder slipped clear of Ngcongca before coolly planting the ball home with a far-post finish to put the men in white and red firmly in control of proceedings.
That left Genk with half an hour to nab the three goals they now needed to turn the tie around. In truth though, they rarely looked like threatening to make even a dent in the scoreline, with guest keeper Sven Ulreich only seriously tested, and not found wanting, by a low shot from Khaleem Hyland in the 84th minute. That effort apart, Stuttgart comfortably saw down the clock to secure their progress.
Genk: Köteles - Ngcongca, Simaeys, Koulibaly, Tshimanga - Hyland, Kumordzi (Barda 61') - Gorius, De Ceulaer (Joseph-Monrose 70'), Buffel (Ojo 77') - Plet
Stuttgart: Ulreich - Sakai, Tasci, Rüdiger, Boka - Kvist, Gentner - Harnik, Okazaki (Holzhauser 77'), Traore (Maxim 75') - Ibisevic (Macheda 83')
Goals: 0-1 Boka (45'), 0-2 Gentner (58')