Long-time Sauber engineer Jacky Eeckelaert is to leave the team at the end of the year and join rivals BAR-Honda.
The Belgian, who is head of vehicle engineering at Sauber, is understood to have made the decision to leave the Swiss team after five years because he wants to spend more time actually working at the track.
Eeckelaert's position at Sauber, when they become the new BMW team, will be taken by Mike Krack, who is currently race engineer for Felipe Massa. Krack's replacement is yet to be confirmed.
The departure of Eeckelaert comes at a time when Sauber and BMW are beginning a massive recruitment drive, with the team believed to be looking to employ up to 100 more staff members.
Most of these additional team members will be put towards a test team, but new personnel are also being drafted in for wind-tunnel personnel, aerodynamicists and model builders.