When the team with the biggest budget doesn't build the quickest car on the grid for 7 years in a row*, heads are bound to roll.
Filling Rory Byrne's shoes was never going to be easy, but under Costa things on the performance side seem to have gone sideways at best, probably backwards. Now they seem to have recurrent gearbox issues on their new car, and I seem to recall failures from a dodgy batch of parts last season.
As with Williams, maybe it is time for a change.
*I know, we can argue about '06 and '07. Not definitively the quickest, though.