Richard Levi says Northants now have to treat every Royal London One-Day Cup game as a knockout clash after their defeat at Durham on Sunday.
The Steelbacks were beaten by 19 runs at Chester-le-Street as they failed to chase down the home side's 291 for seven.
A fine stand between Keaton Jennings (101) and Michael Richardson (68) put Durham in control early on, but the Steelbacks fought back with Ben Sanderson dismissing both men.
Paul Collingwood's unbeaten 53 boosted Durham's total, with Sanderson (3-36) the pick of the Northants bowlers.
David Ripley's men then lost regular wickets in reply, though Levi did make 66 before being run out brilliantly by Collingwood.
Adam Rossington's 69 from 51 balls gave Northants renewed hope, but they had too much to do, eventually falling short.
The defeat leaves the Steelbacks seventh out of the nine teams in the North Group table, with three points from five matches.
With three games to play - the next of which is at home to Yorkshire on Wednesday - Northants are three points off the third and final qualification spot.
And Levi knows how big a task his side now face to make the quarter-finals.
"From the position we are in now we have to treat every game as though it's a knockout," the South African star said.
"We gave ourselves opportunities here but lost wickets at crucial stages."
And on his run out by Collingwood, Levi said: “I don't care how old he is, he is still one of the best fielders around!"
Durham skipper Jennings was delighted with his team's effort.
And he said: "It has been brilliant batting with Michael Richardson. He looks very calm and collected.
"His dot ball count is very low and one of the keys is that we ran really well. It puts the opposition under pressure.
“Then Paul Collingwood pulled us out of a little bit of trouble and he was helped by Paul Coughlin's running.
“It was a good team effort.
"The way we have gone about trying to win each game has been brilliant.”