Six points may be a minimum requirement ahead of tougher tasks to come, but Nicholl also knows the confidence it would bring could change the entire outlook for Northern Ireland – and bring back memories of their successful Euro 2016 qualifying campaign.

"It's great seeing yourself top of the group rather than bottom," he said. "They proved it in the last qualifying campaign and it's the same in this one.

"The players will be sitting there thinking, 'We know how we felt last time'.

"If we can get off to a flyer, get our heads down with Estonia and Belarus away in the summer, it's a chance to accumulate as many points as you wish if you go about your job properly, before we meet the obvious in Germany and Holland."

Thursday's home game against an Estonia side ranked 60 places below Northern Ireland was the easiest on paper, but victory was not always assured as the hosts huffed and puffed through the first half before McGinn broke the deadlock in the 56th minute.

O'Neill said he had done nothing to change his tactics from the same possession-based approach they used during the unsuccessful Nations League campaign, yet Nicholl said minor tweaks had made the difference in the second half.

"We couldn't get (Steven) Davis on the ball, we couldn't get (Paddy) McNair on the ball, George Saville likes to be on the ball but we never managed it," he said.

"That affects the wide men but it just changed in the second half. Craig Cathcart and Jonny Evans were stepping into the game and it was them knocking the ball wide.

"The game just changed dramatically. The wide men were crossing the ball and the wide men were scoring goals."

Nicholl expects a similar approach on Sunday – and similar personnel carrying it out.

Gareth McAuley returned to training on Friday after missing the Estonia match with a hamstring problem, but both Corry Evans (hamstring) and Gavin Whyte (thigh) remain sidelined, and Nicholl cautioned against making too many changes.

"You can make these decisions based on fitness levels, but if you bring one out you've got to make sure the next one is going to contribute," he said.

"We're not going to play them just because they're fresh. You've got to play them because they can do an equal job. I wouldn't like to think there'll be too many changes to be honest."

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