The Gladiators had led through Liam Wilkin's 18th-minute opener shortly after Wrens keeper Alessandro Barcherini had suffered concussion.
Barcherini played on for the remainder of the first half, but was replaced in goal in the second period by Stuart King, with Matt Glass making his appearance to fill the spare outfield slot.
Romaine Graham equalised with a header which may have taken a deflection from a throw in in the 51st minute, and two minutes later Ben Spargo fired the Wrens ahead.
As Matlock tried to hit back King saved well from Chris Bettney's cross shot, then Ben Hunter and Bettney both hit the Rainworth bar in quick succession.
But Matlock punished Rainworth's failure to clear a corner in the 83rd minute when Adam Yates forced the ball over the line.
Young reserve Liam Theakstone played the last 19 minutes, and was instrumental in setting up Fearon's winner with some fine play on the right.
Just 39 turned up on a bitterly cold night to watch, but were treated to an entertaining contest.
RAINWORTH: Barcherini (Glass ht), Fearon, Paling, S. Kennedy, Cooksey (Simpson 62), Hannigan, Toyne, Graham (Cooksey 62), Spargo (Theakstone 71), S. King, Akers. Sub not used: Burton.
MATLOCK: J. Kennedy, Whitcombe (Featherstone ht), Algar, L. King, Yates, Gaughan, Bibby (Harcourt ht, Whitcombe 68), trialist, Wilkin (Nightingale ht), Hunter (Bettney ht), Nelthorpe.
REFEREE: Hristo Karaivanov of Sutton-in-Ashfield.