Sauber's technical director James Key has left the Swiss team to take up a new role in the UK.
Key, who has been with Sauber for two years, did not reveal what the new role was or whether it was in Formula 1.
He said his time at Sauber had been "intense and interesting" as he managed their downsizing from the BMW works team to a private outfit.
Sauber said that Key's responsibilities would be shared by the heads of the four engineering departments.
The team's new car will be launched on Monday 6 February, ahead of the start of pre-season testing on 7 February in Jerez, Spain.