Carmelo Anthony was concerned about Knicks general manager Glen Grunwald making a change to the roster, saying at one point, “If it ain’t broke, don’t fix it.’’ But the star forward couldn’t dispute a minor tinker at Thursday’s trade deadline because the Knicks, who have lost four straight after last night’s 100-98 defeat at Air Canada Centre, actually look broken. Though Anthony once touted Ronnie Brewer in October as the Knicks’ unsung signing, he welcomed with open arms his former Denver teammate, Kenyon Martin, who replaced Brewer on the roster. “If he’s in shape and locked in, I think he can be a big attribute to this team,’’ Anthony said before last night’s defeat. “I’ve been able to play with him for a few years and I know from a basketball standpoint what he brings to the game when he’s locked in and focused. I haven’t talked to him yet. People that I know have spoken to him and say he’s been playing and he’s in shape, ready and focused. As long as that’s the plan, we’re all for it.’’ At Thursday’s 3 p.m. trade deadline, Grunwald shipped Brewer to Oklahoma City to open up a roster spot for Martin, a free agent who hasn’t played all season, but has been working out in Los Angeles and could debut tomorrow against Philadelphia at the Garden. Martin was back in New York yesterday finalizing his physical. That makes six former Nuggets banded together in New York: Anthony, Martin, J.R. Smith, Marcus Camby, Raymond Felton and James White.