Sibierski, 33, said: "I should have signed a new contract there. But Shepherd changed his mind when Glenn had been sacked. It was not the same contract.
"This time it was only 40 per cent of the wages I had been on and it was only one year long.
"The chairman didn't explain anything - he spoke to my agent.
"It was a lack of consideration and respect for me. If I had played rubbish or been injured I could have understood it.
"But I had been playing well for them and I had a great relationship with the fans up there."