Billy Vunipola has revealed his latest injury scare came about after kicking an Aussie Rules ball.
The Saracens No 8, 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," Vunipola 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 could be an integral part of an England group seeking to beat the Springboks in South Africa for the first time since 2000.
England go into the first Test, which is live on Sky Sports, in Johannesburg next week on the back of a four-match losing run, having not won since beating Wales at Twickenham on February 10.
"It is probably a good thing that we have gone through this tough period because it gives us things we can work on," Vunipola added.
"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."