Grand National-winning trainer Donald McCain has been hit by the loss of a sizeable number of horses trained at his Cholmondeley yard in Cheshire for Paul and Clare Rooney.
Reports suggest between 50 and 60 horses are involved, among them Fred Winter Hurdle fourth Starchitect.
McCain, who landed the world's greatest steeplechase in 2011 with Ballabriggs for Trevor Hemmings, told the Daily Mail: "They have decided to move on.
"There have been no disagreements from my end. It is tough. I have had a lot of nice horses for Clare and Paul. We have trained them plenty of winners and they will have plenty more.
"We had a quiet season last season but we trained them 40 winners making them the third winning-most owners in the country.
"It is what it is and we move on."
Currently sidelined rider Jason Maguire is stable jockey to McCain and also retained by the Rooneys.
Asked if his relationship with McCain would be affected, Maguire was quoted as saying: "It is obviously very disappointing the ways things have happened.
"I honestly don't know what will happen."
Maguire said the owners wanted to "spread the risk" and the horses are expected to join existing Rooney trainers such as Gordon Elliott and Ben Pauling, as well as Kim Bailey, David Pipe and Philip Hobbs.