Laravel 5.8多重关系无法正常工作

Question

我有两个模型Team和Match。

Team
-----------
teamId
teamName

匹配

matchId
teamId1  --- belongs to teamId from team
teamId2  --- belongs to teamId from team

关系： =>球队有很多比赛 =>匹配属于团队

我到目前为止所做的是：

匹配模型：

public function teamA()
{
   return $this->hasOne('App\Team','teamId','teamA');
}

团队模型：

public function teamB()
{
    return $this->belongsTo('App\Match','teamId','teamB');
}

控制器：

Match::with('teamA.teamB')->latest()->get();

输出：

{    "data":[{"matchId":1,"teamA":4,"teamB":5,"winner":4,"points":2,"created_at":null,"updated_at":null,
     "team_a":{"teamId":4,"teamName":"team1",
     "team_b":null}}]
}

我想要获得的也是teamB名称，但是不知何故为null。请帮忙。