A knee injury restricted Fitzgerald to just three Magners League starts last season and even though the new injury is on the same knee it is believed not to be linked.
His Leinster colleague Kearney will undergo exploratory surgery later this week to further determine the extent of cartilage damage in his knee, but at this stage it is not known how long the British & Irish Lion full-back could be out for.
Ulster, who sit in third in the Magners League table, will be without Best for six weeks after the hooker fractured his cheekbone.
The 28-year-old will have surgery on the injury tomorrow and will start rehabilitation straight away.
Ireland captain Brian O'Driscoll, Tommy Bowe and Gordon D'Arcy all picked up knocks in the same game and will be monitored this week but currently have not been ruled out of next Sunday's game against Argentina.
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