Thursday's late 3-1 defeat to Holland in Rotterdam means Northern Ireland need to beat the Dutch in Belfast and Germany in Frankfurt next month to have any hope of escaping Group C, but they look increasingly likely to find their way into the play-offs.

"We said to the players, if we are in a play-off situation we will have to come somewhere like this," he said.

"I think the Czech Republic will qualify automatically and I hope they do but we will have to come to a similar opponent, possibly away from home, and win the game.

"And if that is the case we will have to defend for our lives for the last 15 or 20 minutes of the game which we had to do here."

Northern Ireland were cruising at half-time after Paddy McNair's brace either side of a Jonny Evans goal had them 3-0 up, but it turned into a rearguard action after two goals in two minutes from Vladimir Darida and Alex Kral left them hanging on for the final 20 minutes.

O'Neill had switched from his usual 4-3-3 formation to a 3-5-2 for the match, bringing Tom Flanagan into defence alongside Evans and Craig Cathcart at the back, and the Sunderland man got a full examination as the Czechs poured forward in the second half.

"I think we have to take a look (at other options)," O'Neill said. "We have very little time to work with the players and this was a chance to look at three at the back, so we brought Tom into the team.

"It was a strong but relatively inexperienced side with Liam (Boyce) and Gavin (Whyte) up front, Conor McLaughlin coming back in and Jordan Thompson. I think we fielded four players who only have three or four caps each.

"We put experience around them of course, but the most important thing was that those players got accustomed to playing international football at this level, against top players."

The Czech Republic came into the game on the back of a surprise win over England on Friday, the Three Lions' first qualifying defeat in a decade, but the hosts could not build on that as coach Jaroslav Silhavy made 10 changes to his side – with Kral the only survivor.

After Northern Ireland threatened to blow away his side in the opening 45 minutes, Silhavy made four substitutions at half-time to restore a number of senior players, and it made an immediate impact.

However, they could not end an 18-year wait for a win over Northern Ireland, who won the last meeting between the teams in 2017 2-0 in Belfast following three 0-0 draws in recent fixtures.

"It was a good result against a very good team," O'Neill added. "We played them recently for Russia 2018 qualifying, we drew here 0-0 and won in Belfast, but I think this Czech team is stronger than that team.

"They've developed since then so this is a very positive result."