Cape Town - A dispute over money appears to be the reason behind Frans Steyn's decision to pull out of the Springbok squad.Steyn, 27, shocked the rugby fraternity on Tuesday when he pulled of out the Boks' Incoming Series in June.Steyn - who is expected to take up a contract in Japan at the end of the Super Rugby season - said that he wished for time to reflect on his Springbok future.According to the website , Steyn is upset about a promise the South African Rugby Union (SARU) made to him when he returned from French club, Racing Metro, to play for the Sharks in 2012.Due to the dispute with SARU, Steyn is currently earning less than half of what he could have made overseas. It is still unclear exactly what SARU's promise to the player was.Steyn's withdrawal should not come as a surprise though, as it is reported that he already had an argument with SARU during the first Bok training camp in Durban two weeks ago. There he expressed his unhappiness before he got into his car and left the camp.It remains unclear when Steyn will again be available to represent the Springboks.The Boks tackle Wales in Durban on Saturday, with Jan Serfontein expected to be named at inside centre in place of Steyn.