Technical director Mark Smith has left Sauber days before the start of the new Formula One season.
The Briton joined Sauber last July after stints at the now defunct Caterham team, Force India, Red Bull and Jordan.
On Monday, Sauber said in a statement that Smith had "decided to go back to the UK for family reasons".
The opening grand prix of what will be a record 21-race season is in Melbourne on Sunday.
Sauber have struggled with financial problems and were one of three teams paid an advance on their 2016 revenues from the commercial rights holder at the end of last year to tide them through the European winter months.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Despite that, the Swiss tabloid Blick reported this month that Sauber were behind on their February wage payments to more than 300 staff at the Hinwil factory due to cashflow problems.
The team were the only ones not to have their new car running at the first pre-season test in Spain last month, blaming that on a late change in the race calendar after schedules had been drawn up.
Sauber also made the headlines a year ago in Australia when a court ruled they should respect a contract with Dutch former test driver Giedo van der Garde for him to feature for them.
The team had already signed Sweden's Marcus Ericsson and Brazilian Felipe Nasr.
Although Van der Garde won the legal argument he dropped a contempt action pending further talks when it became apparent Sauber team principal Monisha Kaltenborn was determined not to let him race.
Compensation was eventually agreed.
