Fitzgerald, a big-name absentee from last year's World Cup, has instead been included in the second-string Wolfhounds squad to face England Saxons on January 28.
The Leinster winger has been rejuvenated since his failure to win a spot among the 30 that departed for New Zealand and has been viewed as a contender to replace Brian O'Driscoll at outside centre.
O'Driscoll will miss the entire Six Nations after undergoing shoulder surgery, with Keith Earls, Tommy Bowe or Fergus McFadden competing to deputise.
Ulster's Darren Cave, who has been in superb form and was viewed as a leading contender to replace Ireland's skipper, was on Tuesday ruled out for six weeks because of a foot injury.
Scrum-halves Tomas O'Leary and Isaac Boss have both been confined to the Wolfhounds with Boss the only member of the World Cup squad selected for the second string.
Geordan Murphy, who also travelled to New Zealand, is absent from the 24 but earlier this month stated he was available in the event of an injury crisis.
Apart from the injured O'Driscoll and Denis Leamy, all 22 who slipped to a 22-10 quarter-final defeat by Wales last October are present among the senior squad.
They will be joined during next week's training camp in Limerick by the uncapped Ian Nagle, Peter O'Mahony, Tiernan O'Halloran, Paddy McAllister, Andrew Conway and Simon Zebo.
The 22 to face Wales in the Six Nations opener at Lansdowne Road will be named on Monday week.
Alongside O'Driscoll, Leamy and Cave, David Wallace, Felix Jones, Jerry Flannery, Eoin Griffen and Niall Ronan were not considered due to injury.
Ireland coach Declan Kidney said: "It's a new tournament for us and for everybody involved, so irrespective of the highs and lows of the World Cup, it is a fresh and exciting challenge for us.
"The tournament begins what is a big year for us, with a three-Test tour to New Zealand to come in June and ranking points all important for the 2015 World Cup in 2015.
"But for all that, the Six Nations always stands out as high point."
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