Fleming (pictured) signed a three-year deal when he arrived from doomed SPL Team Gretna while Crossley recently penned a new one-year deal which will continue his role as the club's goalkeeping coach.
Sheridan said, "Greg coming in certainly adds that element of competition for Mark and it's an interesting one. Greg will definitely learn plenty from Mark because he is a top keeper who was around at the highest level for a long time. In the second half of the season Mark was one of our best players and I was very, very pleased with his form. He's working very hard in training once again and he is a great lad to have around the place."