England prop Mako Vunipola admits he has had to come to terms with how his body functions in order to avoid further injury setbacks.
The loosehead prop tore his hamstring just half an hour into the Champions Cup final against Leinster in May before undergoing surgery, but he was named in Eddie Jones' 31-man squad for the Rugby World Cup.
The Saracens man was told he needed a "minimum of three months" to recover, casting doubts over his involvement in Japan - but he is remaining upbeat about his chances of proving his fitness ahead of the autumn's global showpiece.
Vunipola missed a big chunk of the Six Nations earlier this year with an ankle injury and then suffered another problem to the same joint, resulting in an aborted comeback.
When asked about his spate of setbacks, the 28-year-old told Sky Sports: "Part of it comes down to the way I play, but luck also has something to do with it.
"The way my body functions has to make up for different deficiencies. This is what [the medical staff] tell me. But my body has been well rested this season. I've had a few injuries, so I've had the chance to work on other stuff.
"I feel good and I'm glad to be back playing rugby."
The visit of Ireland to Twickenham on Saturday, live on Sky Sports Action, as well as the game against Italy on September 6 offer opportunities for Vunipola to gain valuable match fitness.
Jones can make changes to his 31-man squad based on injuries until the official deadline of September 8 - so Vunipola faces a crucial few weeks.
England have been put through their paces by the strength and conditioning team over the past few weeks, and Vunipola believes the side have given themselves the perfect platform to win the World Cup through reaching peak physical condition.
"We spoke about that before we got together," he added. "When the boys came in and had the fitness tests, Eddie said that it was the best he's ever seen, so we've given ourselves a chance.
"The staff here are world class so they've looked after us well. You've seen in the last two games that the boys are looking really fit considering they were pre-season games.
England face Ireland in their next Quilter International on Saturday at Twickenham live on Sky Sports Action. They also face Italy (September 6) in Newcastle as part of their Summer Internationals, all on Sky Sports.