The correct option is A Can't / can
In the given case we need to study the adverb 'well' and its comparative degree 'very well'. The former indicates proficiency and the latter indicates being better in comparison to other things.
"Can't/can" in option A is the correct answer as 'can't' indicates not being proficient at football and 'can' in the second blank indicates being very proficient at ice hockey.
"Could/can't" in option B is incorrect as 'could' indicates the ability to complete an action in the past. This might seem correct, but the second option 'can't' does not suit as it does not need 'very well'. If you are not proficient at a task, then just using the adverb 'well' would be enough. Use of the comparative degree 'very well' indicates being very good at ice hockey. So, this does not agree with the context.
"Could/can" in option C is incorrect as the conjunction 'but' indicate a contrast of the ability. This does not agree with the context.
"Can/could" in option D is incorrect as 'but' indicates a contrast.
Thus, option A is correct.