England will face familiar foes when they bid to book their place in the Champions Trophy semi-finals against New Zealand in Cardiff on Sunday.
Earlier this year, England won a limited overs series in New Zealand only for the Black Caps to turn the tables in England shortly before the Champions Trophy, a tournament for the world's top eight one-day sides, got underway.
England must beat New Zealand to seal a last four spot. If they lose they are out and either Australia or Sri Lanka will go through from Group A after their match on Monday.
If the England-New Zealand match is a washout the hosts will need a low scoring Australia victory to go through. If both matches are washed out, England will qualify behind New Zealand.
"We played a series against them in New Zealand which we won 2-1, we lost the one here 2-1, so it's the decider, I suppose, and it is a 'quarter-final'," Giles said in Cardiff on Saturday after defending his side against accusations of ball-tampering during the Champions Trophy levelled at them by former England captain Bob Willis.
"If you're going to go on and do well in world tournaments, these are the sort of games you've got to win.
"We know the Kiwis are a gritty side, well-organised, well-led, but so are we," Giles, a former England left-arm spinner added.
England, without injured star batsman Kevin Pietersen, have been accused of scoring their runs too slowly.
Jonathan Trott, whom England expect to be fit for Sunday's match against the Black Caps in Cardiff following a quad injury, has found himself in the firing line even though he has scored over 2,500 runs at an impressive average of 52.56 for England in the 50-over format.
Trott played the anchor role in top-scoring for England with 76 at The Oval on Thursday in a seemingly challenging total of 293 for seven that Sri Lanka overhauled during a seven-wicket victory thanks to Kumar Sangakkara's superb 134 not out.
"I don't think it's rocket science," said Giles. "Fifty overs is a long time. You want to set the innings up and give yourselves a platform to build from later on.
"It was disappointing to lose the game the other day to Sri Lanka, but it took an incredibly good innings from one of the best players in the world to do that," he added.
Giles insisted England's approach was no different from that of tournament pacesetters India, the first team into the semi-finals.
"India don't play that much different. They look to set up from the top and then go hard at the back end."
New Zealand have yet to rule out paceman Tim Southee, although he remains doubtful with an ankle injury.
As for the prospect of facing England yet again, Black Caps coach Mike Hesson said: "We've played them six times and it's three-all so we've had some pretty good contests.
"I think both sides will enter tomorrow (Sunday) with a degree of trepidation...I think we're very evenly matched."