Sammy Clingan and Shane Ferguson have withdrawn from the Northern Ireland squad for the games against Scotland and Finland because of knee injuries.
Kilmarnock midfielder Clingan and Newcastle defender Ferguson were named in a 27-man squad on Monday.
Burnley's Daniel Lafferty and Paul Paton of Dundee United have been called up as their replacements.
The friendly against Scotland on 25 March is followed by a Euro qualifier with the Finns four days later.
Ferguson is currently on loan at Rangers and Ibrox manager Stuart McCall was surprised by his inclusion in the original squad announced by manager Michael O'Neill.
|Northern Ireland's remaining Euro 2016 Group F qualifiers|
|Finland (home)||Sunday, 29 March 2015|
|Romania (home)||Saturday, 13 June 2015|
|Faroe Islands (away)||Friday, 4 September 2015|
|Hungary (home)||Monday, 7 September 2015|
|Greece (home)||Thursday, 8 October 2015|
|Finland (away)||Sunday, 11 October 2015|
The 23-year-old joined the Scottish club in January but has not played for the team because of his injury.
"From what I've been led to believe, we won't see him at all this season," said McCall.
Ferguson missed November's defeat by group leaders Romania because of injury and he was one of three players to return to the squad for the two games later this month.
Lafferty, who is on loan at Rotherham United, fills the void left by Ferguson in defence while Paton replaces Clingan.
Goalkeepers: R Carroll (Notts County), A Mannus (St Johnstone), M McGovern (Hamilton Academical).
Defenders: A Hughes (Brighton), C Baird (West Bromwich Albion), G McAuley (West Bromwich Albion), J Evans (Manchester United), C Cathcart (Watford), D Laffert (Burnley) C McLaughlin (Fleetwood Town), L McCullough (Doncaster Rovers), P McNair (Manchester United).
Midfielders: S Davis (Southampton), C Brunt (West Bromwich Albion), P Paton (Dundee United), C Evans (Blackburn Rovers), O Norwood (Reading), R McLaughlin (Liverpool), B Reeves (MK Dons), P McCourt (Brighton), S Dallas (Brentford).
Forwards: K Lafferty (Norwich City), N McGinn (Aberdeen), J Ward (Derby County), J Magennis (Kilmarnock), B McKay (Wigan Athletic), Will Grigg (MK Dons).