@Halagaz ... out of my head : NOT trying to go over mountains (upper drina).
Rather first getting the Macva in a pincer (lower to lowest Drina in the West and Sabac in the East), then from there towards the Kolubara together with a movement into and from the Morava valley, where it goes into the Danube.
@Fehérvári searched abit ... more about Kövess :
You're right, seems he would have made a rather good commander.
Pro for getting the job : he was known to Conrad (served once under the latter), he was an 'upstarter' becoming in his career the youngest Colonel ever in A-H, ... and that despite being protestant also it seemed that old Franz Josef had a like to him, cause in the
Contra :
religious affair in 1912 in Hermannstadt between catholics and protestants the Kaiser backed him, instead firing him, as most others seemed to expect.
However, in 1914, despite being "senior" to many other generals like Dankle, Bühm-Emrmolli he stayed 'just' Corps-commander, not getting command of an army.
Why ?