Comparing a startup (or a company in general) with a professional soccer team is maybe not the best comparison but this way I hope to explain the role of player-coach.
The team is the company management, the paying public are the clients and the public who watch the matches on the television are users who generate advertising income.
There are investors in the company as well in a soccer team. And there is coach who is not part of the team comparable with an advisory board.
The CEO is the captain. The forward is the sales director who need to score with the left and right wing. The rest of the team takes care that sales can sell and that products will be delivered.
There are emotions, traditions and history within a soccer team and a company has its culture and delivers brand value.
If we take my favorite club FC Barcelona as example, the roles are as follows:
Messi is the CEO who leads also the sales with Neymar as his support. Xavi, Iniesta who assist the sales with marketing. Piqué takes care about the operations and support. Valdes is the finance department. And Martino is the advisory board.
A role I prefer to have within a startup is the role of player-coach. So coach the team but also play myself. Playing in a role of mid-mid to assist and defense as the operations.