* The sentence sets up a contrast. The first part says "you like to play baseball" which implies enjoyment. The second part says "can't throw a ball very well" which implies a difficulty.
* "However" indicates a contrast. It signals that the second part of the sentence will present an opposing idea to the first.
The other options don't fit the context:
* "Fact" is a statement, not a connective.
* "For instance" introduces an example, which isn't relevant here.
* "Besides" adds additional information, not a contrast.
The sentence should read: You like to play baseball, however you can't throw a ball very well.