Event driven version

events.cs

///
/// PlayerManager.cs
///


using System;

public class PlayerManager : MonoBehaviour {
  public event EventHandler PlayerDied;
   
  /// ...
  
  public void OnTriggerEnter2D(Collider2D other) {
    if (other.gameObject.tag == "Killzone") 
    {
      var playerDiedSubscribers = PlayerDied;
      if (playerDiedSubscribers != null) 
      {
        playerDiedSubscribers(this, EventArgs.Empty);
      }
    }
  }
}




///
///  GameManager.cs
///

using System;

public class GameManager : MonoBehaviour 
{
  /// ...
  
  public void RespawnPlayer(object sender, EventArgs) 
  {
    sender.PlayerDied -= RespawnPlayer;
  
    var go = Instantiate(/*...*/);
    go.GetComponent<PlayerManager>().PlayerDied += RespawnPlayer;
  }
  
  /// ...
}