The statement has already been clearly made.
It seems, as usual, we just need a reading comprehension check. Admirals, please take a break to smoke the copium now.
Dragon stated, to Sabo, a person who just fought an Admiral on Dressrosa and then infiltrated Mariejoa where there were two admirals in attendance, with whom his commanders clashed and escaped, that the real fight would not begin until God’s Knights are unleashed.
This statement is easily the same level of authority as the description of the admirals as the greatest fighting force, and it was made by a character who has more information.
Comprehension Check:
1) Sabo fought an admiral, and even his subordinates fought an admiral
2) Sabo himself encountered and was wounded by the Gorosei
3) The real fight has not begun
4) God’s Knights are the real fight
Admiral stans will be butthurt until the narrative shows that the force of the GK is superior, then they will just blame Oda or adapt to the truth and pretend they always knew.