Your last paragraph, I don't think there's been a spurs manager in my lifetime who managed to achieve that. Lost count of the Europa League group games/early cup games we've lost against inferior opposition because the second string come in and play appallingly.
Yea, I am not trying to say it is easy task.
It is not!
But also it is very much common sense that you should not rotate 2 of technically best forward players + your best CM of the season. Specially after losing your captain for the game.
I don't claim to know more than Thomas Frank about football. But I did post my version of lineup to matchday thread that would have done much better than the horrorshow that the game turned out to be. (Kinsky; Porro, Danso, VDV, Spence; Palhinha, Grey; Odobert, Xavi, Kudus; Richie) - that lineup would have given rest to Vicario, Bentancur, Sarr, Bergvall - all of who yesterday were ... well.. frankly... awful. Again - awful performances, not awful players.