The Leicester defender has recovered from the knee injury which has sidelined him since early August and is keen to face the likes of Thomas Muller, Mesut Ozil and Toni Kroos in Cologne on Friday night.
Senior men Richard Dunne and John O'Shea are both suspended and St Ledger insists he is ready if called upon by interim boss Noel King.
"I'm as ready as I'll ever be. It's probably not an ideal situation with not having played, but sometimes things can't always be perfect," said the 28-year-old.
"I'm generally quite fit, so hopefully that will stand me in good stead. I have been back training for a few weeks now.
"Obviously I have not played and I am probably fortunate that I am in the squad with the suspensions, so it's down to me this week to work hard, get my head down and try to force my way into the starting XI."
The Germans dished out a humbling 6-1 defeat to the Irish in Dublin last October, but St Ledger is not fazed by the prospect of facing some of Europe's top players.
"These are the games you want to play in as footballers, against the best players and against the best teams and test yourself," said St Ledger.
"When you get results against these teams, it's a great feeling. We are not going out there on Friday just to be losers or to come second. We are going out there to win the game.
"Everyone has come in this week and it's a clean slate for everyone. I'm sure the manager has ideas and it's down to each individual to go out there and prove to him that you want to be in the starting XI.
"Hopefully he will know I have played quite a few times now and that will stand me in good stead, but we will have to see."