Michael O’Neill will risk having key players banned for a World Cup play-off should Northern Ireland need a result in Norway to seal their place.

O’Neill’s team are well positioned to secure one of eight play-off berths having ensured a second-place finish in Group C behind the world champions Germany, who ended Northern Ireland’s four-year unbeaten home run in competitive matches on Thursday. Northern Ireland finish their group campaign in Oslo on Sunday and will kick off with a play-off place confirmed should Bosnia-Herzegovina fail to beat Belgium and Cyprus avoid defeat by Greece on Saturday.

Should results go against Northern Ireland, however, they will need a positive result in Norway to be certain of reaching the play-offs next month and to increase their prospects of being seeded in the draw. They have six players one booking from a one-match suspension. The captain, Steven Davis, and the influential defender Jonny Evans are among the half-dozen who could miss the play-off first leg by collecting a yellow card in Oslo. But with the margins for qualification so fine and resources limited, O’Neill admits he cannot jeopardise Northern Ireland’s chances in Norway.

“We’ll have to see what happens between now and when we play on Sunday,” the Northern Ireland manager said. “You look at the permutations in terms of the teams finishing second. There is no guarantee that 13 points will be enough. I don’t have four players from Bayern Munich on my bench, I’m sure you’ve noticed that, so it’s not that easy to rotate my squad as it is for some other managers.

“There is a real importance to the fact that we make sure of the result in Norway because obviously we want to try and get three points, and we certainly want to make sure we’re not beaten. Equally, we can’t allow ourselves to field an inexperienced team and be beaten and then suddenly lose out on goal difference.

“We’re on a tightrope in terms of the bookings. I thought the players were excellent against Germany and the referee was very good. Both sets of players showed an enormous respect for each other on the pitch, which makes the referee’s job a lot easier. No bookings for either side and we’ll just have to evaluate the situation come Saturday night when everyone else has played.”

Michael McGovern, the Northern Ireland goalkeeper, insists it is “incredibly harsh” that bookings collected in the group campaign count throughout the play-offs. But having avoided any bookings against Germany – Corry Evans, Josh Magennis, Oliver Norwood and Stuart Dallas are the other players on a disciplinary tightrope – he believes “cool heads” can again prevail against Norway.

The Norwich City keeper said: “I think everyone will keep a cool head. In football sometimes you can get booked for small things, especially at international level. It’s been well said the rule is very harsh but it’s the rule so we can’t complain about it. Hopefully we will not get any bookings because they carry on so, even if you weren’t booked against Norway, if you got booked in the first leg you’d miss the second game, which is incredibly harsh.

“We have a small squad and we can’t afford to lose too many players but it would offer boys a chance to step up. I was in that position before Roy [Carroll] got injured and sometimes people just need a chance.

“Even if we go into the game knowing we’ve secured a play-off place, for the seeding we want to go to Norway and win. I thought we were comfortable against them at home and there’s no reason why we can’t win there.”