Gundogan threaded a pass through the Scotland defence to Havertz, who worked it back towards Musiala, the Bayern Munich attacker created himself space to crash a strike into the roof of the net.
Germany were initially awarded a penalty as Musiala went down in a heap after getting caught between Ryan Christie and Kieran Tierney, but referee Clement Turpin deemed the foul occurred outside the area after consulting the touchline monitor.
That merely delayed Germany’s third goal, which did eventually come from the spot following another VAR review that led to Porteous being sent off for a crude challenge on Gundogan, who was chopped down attempting to convert the rebound from his own header.
Havertz calmly sent Gunn the wrong way and drained any remaining optimism from Scotland’s once boisterous and sizeable travelling contingent of supporters.
Scotland tried to limit the damage in the second half, but there was no stopping Fuellkrug’s thumping drive into the top corner within a few minutes of his introduction as a replacement for Havertz.
Fuellkrug had the ball in the net a second time, but fortunately for Scotland they were spared further misery when he was ruled offside.
The only bright spot for Scotland came three minutes from time as Ruediger inadvertently diverted Scott McKenna’s header past goalkeeper Manuel Neuer.
But there was still more punishment to come as substitute Can curled home from 20 yards right at the death to cap a glorious night for the Germans.
