I would say ride it out. If it comes up, it comes up. Dont deny it, or go in to huge details, but be up front and most importantly, be confidant about it. This is how the scenario should NOT go:
Anton: So I hear you are seeing my daughter...
ER: Oh... so and so is your daughter? Well... We have had dinner once or twice... I guess... we are friends... so... yeah I guess we are seeing each other?
He will stab you in the throat, and worship the dark lord in a pool of your blood.
This is how the scenario SHOULD go:
Anton: So I hear you are seeing my daughter...
ER: Yes I am am and she seems to be a great gal. It was kind of a shock to find out that she was your daughter, and I didnt know you played for SL. I like her a lot, and plan on seeing her again.
Look that crazy fuuck straight in the eye and dont hesitate, be confidant, you are not hiding anything. You can be a slimy fuuck, but if he thinks you're not a pu$$y, and will treat his daughter right, he wont come at you.
This advice.
It's sage-like.