According to a source familiar with the situation, North Carolina defensive back Marcus Allen is showing early signs of improvement in his rehabilitation following knee surgery. Allen sustained a partial meniscus tear in his left knee during UNC’s spring break, which has prevented his participation in the football team’s spring practices. The Tar Heels are currently conducting their 15 allotted spring practice sessions, culminating in the spring game at Kenan Stadium on April 20th. “The surgery was successful,” a source informed Inside Carolina on Wednesday. “Rehabilitation is well underway, and…