He should not have been there. He's a prop.
Somehow though, Vincent Debaty managed to pop up on Noa Nakaitaci's shoulder to catch an offload and score a crucial try. This was despite the French winger putting the afterburners on as his side ran the ball out of their own 22.
In a Six Nations that came down to just six points, Jamie Heaslip's try-saving tackle on Stuart Hogg is a moment that we will all remember in years to come. However, credit should also go to Debaty. The prop emptied the tank in scoring that try.