fighters

Since you have seen both fighters, who do you think will win?既然你看到两方竞争者了，你认为谁会赢？

其实这个句子主句为Who do you think will win ，只是它把时间状语Since you have seen both fighters提前了，{do you think 可以看成是主句的插入语}

这个句子也可以这么说，Who do you think will win since you have seen both fighters？