Sasaki could be the first one to be beaten, as his fight with Franky has went on a good length of time, and it doesn’t look like Oda needs to set anything else there up. Enemies don’t always- and in fact often don’t- fall in order in strength.
In Arlong Park, the order went Zoro wins, then Sanji, then Ussop
Alabasta, Nami’s fight came after Sanji’s
Skypiea, of the four priests the third strongest went down first, then the second, then the fourth, and finally Ohm. And there was fights with Yama, Satori’s brothers and Braham all tossed in.
EL, where we had Doriki to tell exaclty how strong everyone was, the order was 4th strongest first for a warmup, then 6th, then 5th, then 7th, then 3rd, 2nd, Spandam, 1st, Spandam again.
TB: Sanji won first, then Usopp, Zoro, Chopper and Robin in a team, Strawhats team up for Oars, Luffy beats Moria
FI: Robin won first, then Luffy, then all the fights concluded in one chapter afterwards where the order was Brook, Usopp, Chopper, Franky, Jinbei, Sanji, Zoro
Dressrosa, Buffalo was one shot well before everyone else. Then Sugar’s sniping. Then the order for the proper fights was Hajrudin, Sai, Cavendish, Barty, Leo, Franky, Kyros, Zoro, Luffy beat Bellamy, Law, Luffy finally winning against Doffy then Sabo beat Burgess after that.
There’s reason to expect that The Calaities will fall in order of Jack, Queen, King, but there could be surprises in the order of the Flying Six
