Joe Schmidt admits he has no idea how Brian O'Driscoll has dredged up the staying power to equal George Gregan's all-time Test appearance record.
Ireland's Kiwi head coach would have considered winning one All Blacks cap "phenomenal", finding himself at a loss for how best to laud legendary centre O'Driscoll.
The 35-year-old will equal former Wallaby half-back Gregan's Test appearance mark of 139, eight British and Irish Lions bows included.
Boss Schmidt will field an unchanged starting XV against England from the side that demolished Wales 26-3, with O'Driscoll having shrugged off a midweek bug.
Hailing O'Driscoll's sheer stubborn will as central to his longevity, Schmidt said he would not bet against the talismanic midfielder guiding Ireland to the Triple Crown this weekend.
"To be honest I didn't play Test rugby so I wouldn't be the best to judge, because I would think one Test would be phenomenal," said Schmidt.
"Where I grew up in a black jersey it would have been phenomenal, so how you manage to amass 130 of them, I'm not quite sure how you do it.
"You have to be incredibly resilient, incredibly talented, a phenomenal professional, and there's your summary: that's Brian O'Driscoll.
"I think he's a very tough character, and the person he is allows him to be the player he's been, and hopefully the player he will be on Saturday at four o'clock."
Should Schmidt's men claim the Triple Crown on Saturday, O'Driscoll will seize his ninth career victory over England, breaking another Ireland record in the process.
Former Ireland and Lions centre Mike Gibson's eight wins over England is under threat then, with Schmidt admitting sometimes he bows to the greater experiences of the wily sages in his squad.
O'Driscoll will retire at the end of the campaign with precious few unfulfilled aims in a startling career.
Schmidt said he never turns down the chance to tap into the decade-plus Test ups and downs of the former captain, and current skipper Paul O'Connell to boot.
"Thankfully I've got a lot of players who've drawn on a lot of experiences at Twickenham itself in the Test arena," said Schmidt, conscious he remains an international coaching rookie.
"We have very much a player-driven environment, they set the standard, I find them incredibly responsive when we're looking at strategy and what we need to deliver technically and tactically.
"But when it comes to directing and controlling the group it doesn't need to be about what experiences I've had, or what I need to bring to the table.
"It's very much their experiences, and there is a good core of experienced players there, so they can lead that and give the younger players the confidence that they've been here before, they know what it takes and they're ready to roll their sleeves up and live with that."