Here's an easier way (for grammar nerds) to think about it: when used in this sense, 恐怕 can't have a subject because it's not a verb.
Look at the example 爸爸恐怕不回家了. There is a subject, but its verb is 回家， not 恐怕 (which, as expected, is in the adverbial position). Let me know if I'm totally off.
Posted on: How to Say 'Probably' in Chinese
March 3, 2016 at 11:12 PMHere's an easier way (for grammar nerds) to think about it: when used in this sense, 恐怕 can't have a subject because it's not a verb.
Look at the example 爸爸恐怕不回家了. There is a subject, but its verb is 回家， not 恐怕 (which, as expected, is in the adverbial position). Let me know if I'm totally off.