Castano won a three-set match for the Flames on court three, Sunday at Radford.
After falling into a 2-0 hole, Radford rallied to take four of the last five singles matches, including a dramatic win on court six, defeating Liberty, 4-3, Sunday at the Radford Tennis Complex.
The Flames (7-12) fall to 0-5 in Big South play with the setback, while the Highlanders (6-13) improves to 3-3 in the conference.
Radford freshman Ratko Varga trailed his No. 6 singles match by a set to Liberty sophomore Alex Poynter. Varga bounced back to seize set two, 7-5. With the Highlanders and Flames overall match tied at 3-3 and Varga trailing Poynter, 5-1, in the third set, Varga completed an improbable comeback by winning six straight games and the match, 3-6, 7-5, 7-5.
Varga's come-from-behind victory lifted Radford to its second Big South win in as many days, after the Highlanders edged first place and previously unbeaten Presbyterian, 4-3, on Saturday.
The Flames commenced the afternoon by winning the doubles point. Liberty Head Coach Chris Johnson used two new pairings, both of which won matches over the Highlanders.
Liberty junior Diego Castano and sophomore Ryker Heller, paired together for the first time in 2016-17, controlled their No. 2 doubles match against Radford's Robin Calais and Alexandros Caldwell, winning, 6-2. The Highlanders won the No. 3 doubles match from the Flames, as Janken Thoen and Samuel Taylor defeated Max Borcuti and Chase Burton, 6-4.
The doubles point was settled in the No. 1 match between the Flames' other new pairing of Poynter and Vince Salas against Radford's Rodrigo Magalhaes and Matko Varga. Poynter and Salas prevailed, 6-4, putting Liberty ahead, 1-0 in the match.
Liberty's lead increased to 2-0, as Burton dominated his No. 1 singles match against Magalhaes. The Flames freshman won in straight sets, 6-0, 6-3, for his sixth victory in the No. 1 slot, this spring.
Radford sliced the lead in half (2-1) with Thoen's straight-sets (6-4, 6-4) triumph on court five over Borcuti. Calais evened the match with Liberty at 2-2 by defeating Heller in two sets (6-3, 6-3) in the No. 4 singles match.
The Highlanders took their first lead of the day, 3-2, with a victory from Caldwell over Salas on court two. Caldwell dropped the first set, 6-2, before rallying for a three-set victory, 2-6, 6-2, 6-4.
On court three, Castano lost a first-set tiebreaker but rebounded to take the final two sets and the match from Taylor, 6-7, 6-3, 6-3. Castano's win squared the overall match, 3-3, prior to Varga's victory over Poynter.
The Flames will play a pair of Big South road matches to close out regular season competition, this week. Liberty will take on Winthrop, Wednesday at 3 p.m., followed by a 1 p.m. match on Thursday at UNC Asheville.