Marussia needs to start beating Caterham on track to ensure it hangs on to 10th place in the Formula 1 constructors' championship, suspects team boss John Booth.
Timo Glock's 12th place for Marussia in Singapore moved his squad into the potentially lucrative final top-10 championship spot on countback of best results.
Marussia appeared to be in danger of losing that position for a while in Abu Dhabi last weekend as Caterham's Heikki Kovalainen ran 12th, before recovering faster cars pushed him back to 13th.
Booth said that acted as a warning that the Marussia/Caterham battle was still wide open.
With both teams needing attrition among the frontrunners to have a shot at top-12 positions, he reiterated that Marussia had to ensure it - not Caterham - was in prime position to capitalise should the final races in America and Brazil prove as dramatic as Abu Dhabi.
"Last weekend's race in Abu Dhabi had us on the edge of our pitwall seats at various points, as it reminded us that to hold on to 10th in the constructors' championship, we cannot control what happens further up the field, ahead of our own private duel with Caterham," said Booth.
"We have to continue closing that gap and find the momentum to get ahead of them on track."
Apart from the Australian GP, when both Caterhams retired, Singapore is the only time this year that Marussia has beaten Caterham in their 'class battle' at the tail of the field.
But Marussia has closed the gap to its rival considerably as the season progressed, and Booth believes his squad's lack of KERS is one of the few areas where it still trails Caterham.
"We've come very close in recent races, despite their KERS-advantage, and we'll remain in dogged pursuit of this objective right up until the chequered flag in Brazil," he said.
Caterham has secured 10th in the standings for the past two years, with Marussia - then known as Virgin - finishing at the foot of the standings for its first two F1 seasons.