Jeff Hendrick, Anthony Pilkington and David McGoldrick are out of the Republic of Ireland's Euro 2016 qualifier against Poland on Sunday.
Derby midfielder Hendrick, who started in the Republic's qualifier defeat by Scotland in November, has a hip injury.
Cardiff's Pilkington has a hamstring problem with Ipswich striker McGoldrick missing because of a thigh injury.
Jonathan Walters, Aiden McGeady, Robbie Brady and Glenn Whelan remain in the squad despite recent injury concerns.
Stoke striker Walters sustained a broken cheekbone recently but wore a protective mask when he came on as a substitute in his club's 2-1 Premier League defeat by Crystal Palace on Saturday.
Walters's club-mate Whelan missed the Crystal Palace game because of a tight hamstring but also remains in contention to play for the Republic.
McGeady may also feature for the Irish even though he was not risked for Everton on Sunday because of a bruised knee.
Winger Brady was out of action for several weeks because of a calf muscle injury but came on as a substitute in Hull's 3-2 defeat by Chelsea on Sunday.
|REPUBLIC OF IRELAND V POLAND MOST RECENT MEETINGS|
|November 2013: Poland 0-0 Rep of Ireland - friendly|
|February 2013: Rep of Ireland 2-0 Poland - friendly|
|November 2008: Rep of Ireland 2-3 Poland|
|April 2004: Rep of Ireland 0-0 Poland|
|November 1991: Poland 3-3 Rep of Ireland|
|May 1991: Rep of Ireland 0-0 Poland|
Hendrick missed Derby's Championship defeat by Wolves on Friday and while McGoldrick and Pilkington are nearing returns to action after spells out because of injury, they will not be ready for Sunday's international.
Uncapped Bournemouth midfielder Harry Arter remains in the reduced 29-man squad after receiving his first call-up.
Arter scored in Bournemouth's 3-0 win over promotion rivals Middlesbrough on Saturday which moved his club back to the top of the Championship.
Newcastle goalkeeper Rob Elliot, Rotherham midfielder Paul Green and Reading striker Simon Cox all drop out of the initial 35-man squad.
Everton duo James McCarthy and Darron Gibson and Burnley defender Stephen Ward were among a number of players who sat out training on Monday but manager Martin O'Neill was not unduly concerned.
"It's not surprising really for James as Everton have played four games in the last 10 or 11 days, Seamus Coleman too. Darron Gibson has a bit of a groin problem - he played yesterday," said O'Neill.
"Stephen has just had a little bit of difficulty. He's had an injury which he is coming back from and he's getting looked at this evening."
O'Neill's Republic side opened their campaign with victories in Georgia and at home to Gibraltar followed by a 1-1 draw in Germany and then the defeat in Scotland.
Poland currently enjoy a three-point lead over Germany, Scotland and Ireland at the top of the table having beaten the world champions 2-0 in Warsaw in October before being held to a 2-2 draw by the Scots.