Kyrie Irving spent a piece of New Year’s Day having an MRI performed on his knee. He went down against the Indiana Pacers yesterday, and he said he “heard something pop.” That’s usually not good, although the MRI revealed a mere contusion, meaning 2013 did not end with yet another potential landscape-altering injury. Al Horford? Out for the season, joining Derrick Rose and Brook Lopez. Russell Westbrook and Kobe Bryant? See you after the All-Star Game — if your rehabs go according to