Billy Vunipola has revealed the reason for his latest injury scare - kicking an Aussie Rules ball.
And the Saracens star, who will head to South Africa on Saturday as part of a 34-man England squad, said he initially did not tell his club coaches.
Vunipola has endured an injury ravaged season, with a hamstring problem being the most recent issue, although he made a try-scoring contribution to Saracens' Premiership final victory over Exeter last weekend.
"I trained fully the week before against Wasps (in the play-offs) and I felt really good, but it was my fault," the powerful number eight said. "I was doing some AFL kicking and then the hammy went tight before the game.
"I didn't tell the coaches that, but when I came off at half-time against Wasps I told them. I was like, 'sorry guys, I was doing AFL kicking'. I stitched myself up there.
"I felt like I was back to normal, and when I feel like I'm back to normal I forget that I was injured and that's probably why I get injured all the time.
"I had to manage myself a bit better the week after. Now I feel strong again, I had a really good start to the week. Hopefully, next week I will train fully and I will be fine."
Vunipola has not played Test rugby since March last year, but he is an integral part of an England group seeking to beat the Springboks in South Africa for the first time since 2000.
England also go into battle in Johannesburg next week on the back of a four-match losing run, having not won since toppling Wales at Twickenham on February 10.
Such a run of results is in stark contrast to the long unbeaten sequence they enjoyed during head coach Eddie Jones' first 18 games in charge.
But Vunipola added: "It is probably a good thing that we have gone through this tough period because it gives us things we can work on.
"We are almost trying to prove ourselves again, which is probably a better motivator than where do we go from where we were before when we won two Six Nations titles.
"Eddie always drives our constant improvements, and it is better to try and improve when you have lost a few games and it is probably tougher on yourself when you are always winning.
"You probably think you are untouchable, and we are not, and it is a good lesson to learn. Hopefully, we can come together as a team on and off the pitch and really take this tour by the scruff of the neck."
And Vunipola has no doubt what to expect from a South Africa team now under the coaching direction of former Munster boss Rassie Erasmus.
"We've just got to scrap for everything," he said. "If we're annoying or making them frustrated, that's probably the best sign of how up for it we are. It means we are in their faces, otherwise they will just bully us off the park.
"That's what they used to do really well, and obviously with a new coach coming in they will just go back to how they used to beat other teams: run over them, beat them up, using their big, physical pack to wear you down.
"Hopefully it's going to be old school, just whose dad is bigger than whose dad. That is the challenge we've got ahead of us, and we've got to embrace it or we will be on the losing side."
