The possibility of the Yankees and Mets competing for a big-name pitcher always puts sizzle into a free-agent chase, but it remains to be seen how deep the two teams get into discussions over rehabbing righty Mark Prior, the ex-Cub. Both have expressed "preliminary interest" in Prior, John Boggs, the pitcher's agent, said yesterday. "But it hasn't been anything more than that. Next week will probably be pretty busy." Boggs says 11 teams have expressed interest in his client, who likely will be ready to pitch in the majors by the end of May.