It was the left middle finger that was giving him some issues.

Per Sixers PR:

STATEMENT FROM PHILADELPHIA 76ERS VICE PRESIDENT OF ATHLETE CARE DR. DANIEL MEDINA:

Robert Covington today underwent successful surgery to repair the extensor tendon in his left middle finger. He first suffered the injury on Dec. 28 at Portland. The procedure was performed by Asif M. Ilyas, M.D., a Rothman Institute hand surgeon and Professor of Orthopedic Surgery at Thomas Jefferson University.

Covington is allowed use of the hand immediately and will wear a splint on the finger while recovering. He will be reevaluated in approximately two to three weeks to assess his readiness to resume basketball activities.

Covington mentioned the injury at last Friday’s exit interview: