I don't know Martinez; is there any reason to single him out for attacks?
I'm beginning to think that there should be something behind-the-scenes.
First of all, from what I know there's been an ongoing rivalry between the Red Sox ( baseball team where Martinez plays) and New York Yankees. Martinex is no doubt one of the best players around and that's even more reason for the Yankees to hate him. Having said that, one has to remember that the Red Sox haven't won the World Series since 1918. The Yankees coach was also slapped around by Martinez last year in one of the many brawls that seem to be happening on regular basis. I think this phrase means "who is the boss?", "who runs the show here?". I think "daddy" means a position of power and that's how the Yankees want to be viewed by others. I think the meaning could also be that of a pimp....someone that looks like a rapper: dressed up in chains, baggy clothes, usually rich, driving fancy cars, etc...again, same idea...person of power and influence.
Cassell's slang disctionary has an explanation for that word as well and the one that I think suits best says:
"the most important, powerful, the supreme example, best known".