It is a riddle, wrapped in a mystery, inside an enigma; but perhaps there is a key.
That key may be the gentle encouragement given to him by Steve Evans, who insisted Doukara had earned his place on the bench through hard work, and he was only selected as an option because he was a legitimate option.
Frequent watchers of the Under-21s will say, with all the requisite caveats, that when he looks interested he tends to be one of the best players on the pitch.
His introduction from the bench in the 30th minute turned the game, contrary to all expectations.
A year ago Doukara was a first team regular, but his absence has been justified since this point in 2014.
If he can have a similar impact to the one he did last night, he could prove an asset. That is more than anyone would have said as recently as Wednesday.