Northern Ireland manager Michael O'Neill has hinted that he may further tinker with his side's formation for the visit of Slovenia on Monday evening.

The 46-year-old started with a 3-5-2 set-up against Wales in the 1-1 draw at the Cardiff City Stadium, before switching to a more familiar 4-3-3 later in the game.

O'Neill was not completely happy with the attacking performance of his side in South Wales, however, and is now prepared to alter things once more in preparation for this summer's European Championship.

"We were a little bit disappointed that maybe we didn't have more of an attacking threat with that system," he is quoted as saying by The Guardian. "I think the two lads up front worked very hard. It's the first time they've played together and Kyle [Lafferty] hasn't played much football. There are mitigating factors in that.

"There's always comfort as a coach and a manager when you say you're going to change to four. We threw Jonny [Evans] in at left-back and he doesn't bat an eyelid and we played in the 4-3-3 and are able to deal with it. It's exactly what we want. In the summer we are going to have to be flexible.

"Either system has strengths or weaknesses depending on how the game's going. The most important thing between now and the end of the summer is the players are able to adapt it and understand it very quickly and the game on Thursday night gave me a lot more confidence that that's the case."

Northern Ireland follow up the friendly meeting with Slovenia by taking on Belarus and Slovakia in their final warm-up fixtures ahead of Euro 2016 later this year.