Wigan Athletic's Will Grigg and Liam Boyce of Ross County are included in Northern Ireland's squad for the friendly against Belarus in Belfast.
The two strikers are battling for what is thought to be the one remaining attacking berth in the 23-man panel for the Euro 2016 tournament in France.
Both 24-year-old Grigg and former Cliftonville man Boyce, 25, have been in fine scoring form this season.
The squad will be announced on 28 May, the day after the game against Belarus.
Northern Ireland then play Slovakia away in their final Euro 2016 warm-up game on Saturday, 4 June.
If former skipper Aaron Hughes plays against Belarus he could win his 100th NI cap in the Slovakia fixture.
Northern Ireland face Poland in their first Group C game on Sunday, 12 June in Nice.
Grigg has seven caps and last played for Northern Ireland in a challenge match against Qatar on 31 May last year.
This season he was top scorer in League One with 25 goals as Wigan secured the League One title.
Kyle Lafferty, Conor Washington, Jamie Ward and Josh Magennis are thought to be the strikers sure of inclusion for the finals in France.
Washington scored the goal in Northern Ireland's 1-0 win over Slovenia in Belfast in March.
That victory saw Northern Ireland go 10 matches unbeaten, which is the longest run in Northern Ireland's history.
"We will use the Belarus game to look at our options, our systems and how we play," said manager O'Neill.
"It's also a chance to look at personnel and to give players opportunities.
"We are on a good run at the minute and we want to continue that run.
"It is important that we approach the match in the same way as we have approached all our other games since qualification.
"In those we are unbeaten. We have won two and drawn one. We have only conceded one goal and that was from a penalty."
Northern Ireland squad: A Mannus (St. Johnstone), M McGovern (Hamilton Academical), R Carroll (Notts County); C Cathcart (Watford), J Evans (West Bromwich Albion), G McAuley (West Bromwich Albion), L McCullough (Doncaster Rovers), C McLaughlin (Fleetwood Town), L Hodson (MK Dons), A Hughes (Melbourne City), D Lafferty (Burnley), P McNair (Manchester United), M Smith (Peterborough United), S Davis (Southampton), O Norwood, (Reading), C Evans, (Blackburn Rovers), S Ferguson (Millwall), B Reeves (MK Dons), S Dallas (Leeds United), N McGinn (Aberdeen), W Grigg (Wigan Athletic), K Lafferty (Norwich City), C Washington (Queens Park Rangers), B McKay (Dundee Utd), L Boyce (Ross County), J Ward, (Nottingham Forest), C Baird (Derby County), J Magennis (Kilmarnock).
|Northern Ireland's Euro 2016 Group C fixtures|
|Sunday, 12 June (Nice, 17:00)|
|Thursday, 16 June (Lyon, 17:00)|
|Tuesday, 21 June (Paris, 17:00)|