Now aged 28, Castaignede has not started a match in the competition since the French beat Italy 42-31 in April 2000 because of the Achilles he ruptured later that year during a warm-up session.
So now, after warming the bench for the first three RBS 6 Nations matches of this season, Castaignede admits he will be in no position to bark the orders on his return to the team.
He will listen studiously to his team-mates, take orders willingly, and fall into line with all commands.
After four operations on his Achilles, he is just thrilled by the prospect of pulling on a blue jersey again.
"I am so happy," he said. "Being on the pitch is an extra chance for me, I was impatient.
"I have been with the squad since November. I was relegated to the bench at the start of the RBS 6 Nations and I was a little bit disappointed. But I knew that it would happen at some point."