Celtic's strength in depth meant they could beat Rangers with three of their most dangerous players spare.
Celtic were made to fight for their win against Rangers at the weekend, as they battled with 10 men to earn a 3-2 victory.
Striker Odsonne Edouard came off the bench to score a winner he will treasure forever, his first Old Firm goal.
Rangers were at least competitive, and will take encouragement from their win heading into next month's semi-final.
But one further glance at Celtic's bench should give them cause for worry.
This was Celtic with 10 men winning away to Rangers, and leaving three of their most dangerous attacking players on the bench.
Celtic felt they could afford to leave Scott Sinclair, Charly Musonda and Patrick Roberts as unused substitutes, and the move paid off.
Sinclair has scored 42 goals in two seasons for Celtic since joining, while Roberts hit double figures last season before injury interrupted his latest season at the club.
Musonda is on and 18 month loan from Chelsea and is tipped to prove why he can be a top international star, but Celtic felt they could do without all three of these players against Rangers.
Their decision not to introduce another winger may have been influenced by a need to re-shuffle defensively after Jozo Simunovic's red card.
Even so their ability to win a man down without the dynamic trio on the pitch is a frightening show of depth, which bodes well for their chances of semi-final success when the two teams meet at Hampden.