England captain Dylan Hartley accepts that one more concussion could force him to take an extended break from the game or even end his career.
Hartley has missed 14 weeks of the season over two spells after taking blows to the head, the most recent of which came in the final match of the RBS 6 Nations when he was knocked unconscious in the Grand Slam-sealing victory over France.
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Debilitating lethargy was the main symptom of his latest absence and he was only able to return in Northampton's final match of the season on May 7, making Sunday's Test against Wales at Twickenham the second outing of his comeback.
Now the 30-year-old hooker is symptom-free and feels "strong and fit", but he knows a further concussion might have far-reaching implications.
"If I got another lay-off now, I'd be worried. I'd probably start looking at other careers or maybe a long lay-off. Maybe I'll look at my tackling technique too!" Hartley said.
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"I'd have to ask a specialist. Three in one season would warrant a bit of time off and I would probably take that anyway - take a step back and have a minute.
"It's not something I fear, it's something you deal with when it happens. I won't go into the Wales game worrying about it. I feel confident in my head and have tested it out a few times."
A frustrating period of uncertainty in which Hartley waited for the symptoms to lift so he could begin the return-to play protocols was notable for his need to sleep and inability to complete tasks.
"Basically all I did was mill about. I felt a bit useless, a spare part. And when you stop training you de-condition, you get negative, you feel bad about your body," Hartley said.
"I couldn't run or do anything and spent a lot of time on the couch. It was lethargy, constantly wanting to sleep.
"I'd wake up in the morning, have breakfast and go back to bed, or go into the club to attend a few meetings and then go back to bed. I just didn't have any get up and go.
"It's really weird, I actually went to use my bike at home thinking 'right, it's been a month now and I've done absolutely F-all, I'm going to go and get on my Watt bike'.
"I put all my kit on, put my water bottle on and I just said to myself 'get on the bike'....and I just couldn't get on the bike.
"I had no urge to get on the bike. I almost tried forcing myself to get on and I just said 'I can't be bothered', so I went back to lie on the couch and went to sleep.
"There's no lying in your recovery. I had a constant reminder of that every time you see your kid and you think 'if I hit my head again, what's that going to mean?'.
"Then I just turned the corner one week and it was great to get that run-out against Gloucester for a bit of confidence."