In every installment of FIFA game, including FIFA 17 and FIFA 18 in Pro Clubs you can control all players on the pitch even if you don’t have 11 human players.
This is possible by using the ANY position. One player chooses to play as ANY and then he controls all players that aren’t controlled by other human players. He controls his own pro player aswell and AI bots that would normally be controlled by an artificial intelligence built in FIFA game.
In the matchmaking lobby you can choose to opt in or opt out to play with other clubs that play with ANY player. Most teams don’t want to play against ANY, as this can be hard if the ANY player is decent at the game. This can ba a little unfair if the team has only like 2-3 players, so be sure to consider it while playing.
ANY position can be filled only if there are at least one other player in the lobby. You can play with ANY even if you have 10 other human players, but then there’s really no point, you can just choose the one position that you’re going to play on.
Some players decide to play as ANY because the AI bots in FIFA can be really frustrating, but make sure you’re up for it and know that you might encounter less teams by doing so.