Springbok lock Juandre Kruger will leave the Bulls after the 2013 Super Rugby season to join French club Racing Metro 92, the Pretoria union announced on Tuesday.
Bulls head coach Frans Ludeke admitted it was difficult for South African franchises to match the financial offers made by European clubs.
"It is always good to know and to hear that your players are wanted all over the world, but unfortunately it is not always possible to hold on to them once those offers start coming in," Ludeke said.
"With the exchange rate as it is at the moment, it is very difficult to remain on level terms with those clubs when it comes to contract talks."
While the Bulls were eager to extend Kruger's contract, Ludeke said it was not possible due to financial constraints.
"We are very happy for Juandre, as it is a great offer he received, but that left us in an unfortunate position that we could not match it."
Ludeke believed Kruger still had plenty to offer the Pretoria outfit in next year's Super Rugby competition.
"Juandre is a real pro and I know we can still expect a 110% effort from him.
"We sat down as a group recently to discuss our goals and objectives for 2013 and I am very confident that we will get an exceptional contribution from Juandre right till the last game of our season."