The inclusion of Hale, along with young strikers Dale Taylor and Lee Bonis, meant O’Neill opted to leave experienced striker Josh Magennis out of the squad.
Magennis, who is playing for Exeter City in League One, has scored 12 goals in his 82 international caps.
“I’ve not brought Josh on this squad because to bring Josh away at this stage of the season and not to utilise him wouldn’t be the right thing for him,” O’Neill added.
“He can have a little bit of a break, but it also gives me the opportunity to have a look at the likes of Lee Bonis, Dale Taylor and Ronan Hale.
“It’s important that there is a transition in all squads, but the players who are left out are still very much important players for us.”
O’Neill added it was “a very important year for us” after a positive 2024, when Northern Ireland won their Nations League group in League C.
NI will face Slovakia, Luxembourg and the winner of Germany’s Nations League play-off with Italy when 2026 World Cup qualifying begins in September.
“We come out of a good year where we made a lot of progress, particularly with a lot of the young lads and the potential that they have.
“These games in March and June give us the opportunity to look at the squad and prepare the squad in the best way possible for what the challenge will be in September.
“You have to move the squad on. It’s important that we do that.”
