How do player-managers substitute players in football?

Question

First of all, player-managers, when they play, should focus solely on the game - and not individual players - to be effective, so they shouldn't be able to know exactly how well individual players are performing or even how well their plan is working in different parts of the pitch. On which basis, then, does a player-manager make substitutions?

Secondly, in order to substitute someone on or off, they need to give a signal to the assistant referee (or, more likely, to the assistant coach) so that they know who is being substituted. However, depending on the player-manager's position, they could be far away from the both the assistant referee and the assistant coach, and it's unlikely that they would be able to afford to temporarily leave their position just to make a substitution. Therefore, question two: how can a player-manager give the right signal for substitution?

And, finally, there is of course going to be bias in that the player-manager probably won't want to sub themselves off, and that they will be more likely to sub off players whose decisions they don't like (e.g. a player didn't pass to them). And so, final question: how do they deal with that bias.

Answer 1

First off, a playing manager is not blind. Even on the pitch they'll see who performs and who doesn't. And they'll quite frequently communicate with their assistants.

Anyway, there are several ways of managing subs:

• Halftime. 15 minutes are more than enough to talk to the team and the assistant. Upcoming subs can be discussed here already as well as under performing players or health issues, etc. so the assistant knows when to bring them in without having to wait for a signal.
• Hand signals. They're pretty effective in loud environments or far distances.
• Shouting. Like a manager can shout at the players from the coaching zone this also works the other way round.
• Use breaks. When the ref needs to write something down (another sub or a card) or during an injury break or when the ball has gone over the roof there's also enough time to quickly discuss matters with the assistant.
• Let the assistant decide. If you trust your assistant you can have them manage the subs without requiring your permission. Especially easy subs don't require the manager's permission (e.g. because of an injury).
• Thumbs up. The assistant suggests a sub and the manager just answers with a thumbs up or down. Easy and effective.

And about bias: Yes, it can happen that the manager stays on the pitch and subs someone else off instead of himself. But that can be caused by several reasons and isn't necessarily a biased decision. Players should always trust their managers to make the right decisions, whether they're on the pitch or in the coaching zone. If you don't trust your coach you're in the wrong team. Period. There's not much you can do to prove bias anyway. Also substituting someone off because of one wrong pass is stupid and no manager in their right mind would ever do that. Intentionally weakening the team by wasting a sub and eventually replacing a good player with a worse one should be a very rare exception.