I think you may try something like this:
$teams = Team::with('users')->get();
return View::make('team/addplayers', compact('teams'));
In your view:
@foreach ($teams as $team)
@foreach ($team->users as $user)
<p>
{{ Form::checkbox(
'player[]',
$user->id,
(in_array($user->id, $team->users->fetch('id')) ? 1 : 0)
)
}}
{{ Form::label('email', $user->email) }}
</p>
@endforeach
@endforeach