に in コントロールに苦しまなくなった

Question

コントロールに苦しまなくなった野球系YouTuber

You would want good control as a pitcher so, "to become not-suffering in control" or "attain good control" is the default way of reading this.

but what exactly is コントロールに? i have to resort to reading it as コントロールは/が...

thanks

Answer 1

This に marks the cause/reason of one's feelings or pychological reactions. For example:

• Aに驚く　to be surprised at A
• Aに悲しむ　to feel sad about A
• Aに怒る　to become angry with A
• Aに戸惑う　to be puzzled by A
• Aに感動する to be moved/impressed by A

So コントロールに苦しむ means "to suffer from (one's bad) control". コントロールが/は苦しむ means something like "(Mr.) Control suffers", which makes no sense here.