You could have the best defence coach in the world sitting in the stand.
Possibly, the chap in question could have access to surface-to-surface missiles and 25 hand-picked marksmen dotted around the stadium.
But when Louis Rees-Zammit is in full-flight there would still be no guarantee of stopping him.
The Wales wing tuned up for the Six Nations next weekend with one of the tries of his career as his club Gloucester defeated Newcastle Falcons 32-22 at Kingston Park.
It was 12 seconds and 78 yards of undiluted quality, the rugby equivalent of a wonder goal from Roy of the Rovers in the pages of Tiger and Scorcher circa 1975.
Watching from the BT Sport commentary box, Austin Healey said: “That is amazing. That is truly sensational.
“The only problem with this guy is he’s not English.”
The score saw Rees-Zammit field a Newcastle kick near his 22, then start running left before slicing back between two defenders.
Spotting two more would-be defenders ahead, he ran towards them only two veer clear with seemingly effortless acceleration which Brett Connon and Sam Stuart could do nothing about.
“In a game like this, when defence are a little bit more open, he can be so dangerous,” enthused Healey.
“What an example of how to score in open space and how to create it for himself.
“He runs into cover, then he runs away from it.”
Rees-Zammit had appeared as a replacement in the 54th minute. By the time the game was over he’d made 104 metres with ball in hand, made two clean breaks and beaten seven defenders, as well as scoring his try.
Of his 62nd-minute touchdown, Gloucester head coach George Skivington said: “That was special. Sitting on the bench and coming on when he did is tough.
“But he had a couple of good moments and an outstanding try.
“He’s good to go (for the Six Nations) and playing like that is great timing for Wales. We’ll lose Zam for a good period but I hope he goes well for Wales.”
On social media, someone called Rees-Zammit unreal while another post settled for classing him as different gravy. His try — well, his try was widely billed as unbelievable.
This week, the lad from Penarth turns 21.
What a way to celebrate.
And it's great news for Wales as they head to Dublin for the Six Nations opener away to Ireland.
Wales are defending champions and are being widely written off. If they are to achieve anything significant in this year's tournament, then Rees-Zammit will undoubtedly be key.
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