Fitzgerald is no stranger to the treatment table and a recurring hip and groin problem reared its ugly head on Sunday, while the reigning GUINNESS PRO12 champions were warming up ahead of a clash with Benetton Treviso.
In his absence, Leinster went on to draw 24-24 in Italy, leaving them fifth in the GUINNESS PRO12 table after eight rounds.
But Cullen, who made 122 league appearances for the Leinstermen before retiring this summer, insists the club will not have to stomach the disappointment of injuries forcing Fitzgerald to also call it a day.
"He is a resilient guy," Cullen told the Irish Times. "He's come back from a pretty major neck injury which you would think would be of more concern. He has come back from that and had no problems.
"It is just about managing it and doing the best for him. It wasn't worth taking a risk. On another given day with a different individual, we might have taken a different course of action. But, we've been conservative with Lukey.
"If you play rugby, it is an occupational hazard. It is probably something you always have at the back of your mind because it's a tough industry. That is the reality of the game.
"Eoin O'Malley is not in the game anymore because he's retired. He got one knock. Everyone would have said he's the most likely guy to be Brian's (O'Driscoll) replacement if you wind the clock back five or six years ago and he was retired before Brian."
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