Paul O'Connell believes "the best lineout forward in the world" Victor Matfield is better now than when he quit rugby for two years in 2011.
Ireland captain O'Connell hailed Springboks stalwart Matfield for adding extra steel to the South African ranks that had been missing during his temporary retirement.
The oldest Springbok of all time at 37, Matfield quit the game entirely after Rugby World Cup 2011, only to be enticed back to both the Super 15 and Test arenas.
Matfield praised O'Connell as "the best player I've played against" earlier this week, ahead of Ireland hosting South Africa in Dublin on Saturday.
Munster talisman O'Connell said no amount of love-ins will detract from the brutal task facing Joe Schmidt's Ireland side in the Aviva Stadium Test.
"I think he's the best lineout forward in the world and has been for a long time," said O'Connell.
"To be able to take two years out, come back and be as good as if not better than he ever was is an incredible achievement.
"He still seems to be using pretty much the same system he has used for seven, eight, nine years, the same lineouts, and teams just can't come near him on his ball.
"You see in that New Zealand game the amount of lineouts that South Africa upset all across the board, not just Victor Matfield, but Vermeulen as well.
"I think it contributed massively to the result: if you can't be sure of your own ball when you go to the touch, to start plays or exit from your half of the pitch, it's a really tough way to play the game.
"I think it's probably something South Africa have been missing in recent years, and he's brought it back with abundance.
"He has a fantastic record as well, having beaten us on the Lions tour in 2009, having won a World Cup in 2007, his record in the Super 15 too, he's a fantastic player.
"I was delighted with the compliment he gave me, but it's all irrelevant come tomorrow afternoon."
South Africa edged past New Zealand in Johannesburg 27-25 last month, inflicting just the All Blacks' second defeat since claiming the World Cup on home soil in 2011.
Young fly-half Handre Pollard has been credited with helping coach Heyneke Meyer add an expansive attacking edge to the Springboks' naturally-aggressive tight play.
Munster's 35-year-old lock O'Connell has warned Ireland to steel themselves for one of their toughest physical assaults yet, despite South Africa's improved wide threat.
"They are different in a better way, so many of the things they do I recognise from a few years ago," said O'Connell.
"They still have an excellent maul, they score numerous tries from that.
"It's very effective for them in terms of exiting as well.
"They are very good at the back of the lineout and putting their centres and wingers into midfield, and putting teams under pressure that way.
"So you recognise that from the past, and they are still strong there.
"But the way they've been playing with ball in hand recently, I just think they've an extra string to their bow that they maybe didn't have when they won the World Cup, or they didn't maybe use then or in 2009.
"So it makes the challenge even bigger again."