Sauber's head of track engineering Tim Malyon has left the Formula 1 team after just over three months in the job, Autosport has learned.
The former Red Bull engineer joined the team in January as a replacement for Giampaolo Dall'Ara.
But his last race was the Chinese Grand Prix and he will officially leave the team at the end of the month.
It is the second high profile departure for the Swiss team after technical director Mark Smith left on the eve of season.
Malyon cited personal reasons for his departure.
Paul Russell, Felipe Nasr's former race engineer, moves into the role of chief race engineer on an interim basis.
Sauber has not paid its staff on time for the last two months because of cashflow problems, with boss Monisha Kaltenborn working to find more backers.
Marcus Ericsson's Swedish sponsors stepped in with an early payment to ensure staff were paid for the month of March, albeit eight or nine days late.
Kaltenborn has conceded the team's financial problems are holding up developments it has planned for its 2016 car.
However, funds were available to ensure Nasr will get a new chassis for this weekend's Russian GP having been blighted by handling problems so far this season.
The Brazilian said the problems were not evident in pre-season testing, when he used chassis 01, the one team-mate Marcus Ericsson has used since Melbourne.
But Nasr has struggled in all three of the races so far this season.
Sauber ran identical set-ups on Nasr and Ericsson's cars in China but the problems continued and as a result, Nasr has been given chassis 03.
It is understood the team is very short on spares.