That is how Marler reflects on the first 20 minutes of England's second Test against South Africa in Johannesburg during the summer, when the Springboks rampaged into a 22-3 lead.
The pace and power at which South Africa set about England at Ellis Park was a rude awakening for Marler in his second Test. He suddenly knew what international rugby was about as England went on to lose 36-27.
He said: "Those 20 minutes will stay for me for the rest of my career. South Africa were hammering us and I thought 'unless we pull our fingers out we will get 50 points on us here'. That was when I realised 'this is a step up'.
"But it is good to have those moments as reference points. You think 'that is how I want to make someone else feel' because I don't want to experience that again."