const players = this.state.players.map(player => {
        return { ...player, updated: player.id === id };
});
this.setState({players: players});

updatePlayer = id => {
      const players = this.state.players.map(player => {
        player.updated = player.id === id ? true:false;
        return player
      });
      this.setState({players: players});
  }

updatePlayer = id => {
    const playerObj = this.state.players.find(item => {
      return item.id === id
    })

    if (playerObj) {
      playerObj.updated = true

      this.setState({ playerObj })
    }
}

this.state = {
    players: [p1, p2 ,p3, p4], // each p is a player.
    //notice that playerObj is now a reference to some of the P on the players array
    playerObj: {
        ...playerstuff,
        updated: true
    }
}