Disclaimer: This article and video makes references to suicide.
But as he can testify, trophies and the lifestyle of being a professional footballer do not make players immune to the stresses of the job.
And he has revealed how those worries affected him in a candid conversation with broadcaster and Arsenal fan Roman Kemp for Mental Health Awareness Week.
"I've been affected by thinking, 'What am I doing here, when does it all stop?'" Mertesacker says. "I recall team-mates saying that I told them that I'm going to stop at 27 because I predicted the pressure and what is on you.
"I was vomiting before games. It's crazy when I think the amount of pressure that needs to be released."
"We need to make sure that we have a group of people that stand strong together"
Mertesacker is painfully aware of the tragic consequences of mental-health struggles, having lost friend and team-mate Robert Enke to suicide in 2009.
"He was one my closest friends and when I look back, I think why have I not done more to support and help him," he says.
"We all have to live with these things because we feel some kind of guilt. But we also need to back ourselves up. I had conversations with him and I thought I was a safe space for him.
"I was hoping to make a positive impact, but what is it about footballers that people want to constantly hide something from the public? Because everyone feels that it can weaken your position."
Now as Arsenal's Academy manager, Mertesacker looks after the development of younger players in his care, both on and off the pitch.
The holistic development of Academy players is a key strand of the Elite Player Performance Plan (EPPP), with Premier League rules ensuring players at all clubs, from the Academy upwards, receive a variety of support for their mental health from their clubs and the League.
"We need to make sure that we have a group of people that stand strong together, that's what we believe," Mertesacker says. "We should be in a position where we open up to our feelings and make sure that we let it out in order for us to be more free on the pitch.
"There will be disappointing moments, there will be releases from the Academy, there will be losses, where we have to pick ourselves up again. But the conversation around it is absolutely key."
To access the Premier League's growing library of expert advice and top tips from players to support positive mental and physical health, visit our #StayWell hub.
Part 1: UK football family reaffirms commitment to mental health
Part 2: McAtee: Team-mates can help your mental health
Part 3: Lennon: I didn't realise there was so much help around
Part 4: Mertesacker: Wellbeing support is crucially important
Part 6: Premier League managers unite to tackle suicide
Part 7: Ruddy: Mental health project helps people let off steam
Part 8: Kemp: Opening up helped my mental health
Part 9: 'Saints Foundation has been a lifeline for me'