Much of the talk ahead of Friday night's World Cup qualifier in Stockholm has centred on Paris St Germain striker Zlatan Ibrahimovic and his potential to wreck Ireland's hopes of claiming the runners-up spot in Group C.
The 31-year-old has 33 goals already this season, four of them in Sweden's 4-2 friendly victory over England at the Friends Arena in November.
St Ledger said: "I have played against a few decent strikers in my time. He is up there.
"He's a very, very good striker. I think you could probably put him in a category with people like Messi and Ronaldo. He can win games by himself with magic moments.
"He showed that against England and he is a very, very good player."
Ibrahimovic's talent is well-known, but his critics argue he blows hot and cold.
St Ledger said: "Let's hope he has a cold one this week.
"To be honest, I have not seen too much of him. I wouldn't say I have watched loads and loads of games of his over the full 90 minutes, so it would be very harsh for me to judge him on that.
"You only see clips and nine times out of 10, he's brilliant."
Ireland boss Giovanni Trapattoni and his players flew out to Scandinavia this afternoon having completed the bulk of their preparations, and there is little doubt that Ibrahimovic would have come high on his list.
But St Ledger admits the Swede is far from the stereotypical big man up front.
He said: "When you play against big players, seven times out of 10 you would probably say they wouldn't be too good with their feet or they wouldn't be as mobile.
"But he seems to have the full package. He is obviously very physical, and he's got the feet. He seems quick enough over the ground, so he has got everything.
"Obviously, he's a very good player - you can't take that away from him. You give him the respect he deserves and then you just try to play your normal game."
St Ledger is back in the Ireland fold for the first time since a five-month injury lay-off with a hamstring problem which eventually prompted a visit to renowned specialist Hans-Wilhelm Muller-Wohlfahrt.
His lack of recent football - the 28-year-old has just two competitive games for Leicester under his belt since his return - means Aston Villa's Ciaran Clark is marginally ahead of him in the race to partner John O'Shea at the heart of Trapattoni's defence in Stockholm.
He met up with the rest of the squad in Portmarnock on Sunday, which was not only St Patrick's Day but also the Italian's 74th birthday.
Asked if he had bought his manager a birthday card, St Ledger replied: "I gave him a birthday kiss. I thought that would do the trick."
The pair were seen deep in conversation as the squad embarked upon a gentle walkabout at their Gannon Park training base, but the defender revealed they were not talking about a potential role in Sweden or cunning tactical plans.
He said: "We were talking about the Pope - I am being serious. Honestly, we were talking about the Pope.
"I think the manager was saying he knows the Pope - unless we have got mixed up in translation."