Somerset Rebels have released Jay Herne from his deal with immediate effect.
The Australian has ridden infrequently because of his contract with parent club Bournemouth Buccaneers.
"This situation is not of Jay's making. It is the result of a congested fixture list and riding in two leagues," said general manager David Croucher.
Croucher added he was "saddened" by the inevitable decision and that despite Brendan Johnson's ability it was "too early" for him to replace Hearne.
"This again is no criticism of Brendan and we fully expect him to develop his talent, and feel sure he will be a big part of the Rebels' future in years to come," added Croucher.
"With the new averages coming into effect we have around 5.20 points with which to find a replacement for Jay, and we are actively seeking a suitable rider to strengthen up the team for the remainder of the season.
"In the event that no such rider becomes available immediately, we have a contingency plan in place to bring a temporary replacement on board."
Meanwhile, the Rebels finished runners-up for a second successive season in the Premier League Pairs Championship.