I think most everyone is misinterpreting how he’s using the word. Messi is among those that can single handedly dictate a game the most, AKA he is outsized influence on outcomes of games. Considering there are 11 players in each team he is the most influential.

I take it as “most influential single player on outcomes/dominance of teams”. He is the player that can single handedly exert the most influence on a game. Certainly true in the modern era and if you consider his longevity it’s hard to argue against the same for all time.