The 33-year-old, who is retiring at the end of the season, has been eased out of the Gunners fold by manager Arsene Wenger as he prepares to enter a management role with the club next season.
Mertesacker told Der Spiegel that his "stomach turns round" ahead of a game, while he also comes close to vomiting.
"Some days you realise that everything is a burden, both physically and mentally, but you have to deliver without a doubt, even if you are injured," the defender said.
"In the moments before a game starts, my stomach turns around as if I had to vomit. Then I have to choke so violently until my eyes water. Even if I had to vomit before every game and go to rehab 20 times, I would do it all over again. It was worth it for all of the memories.
"My body is finished. Everyone says I should enjoy the last year, to play as much as possible and take everything in, (but) I would rather sit on the bench or - even better - in the stands, and then, for the first time in my life, aged more than 30, I will feel free."
Arsenal play Watford in the Premier League on Sunday looking to build on their Europa League victory over AC Milan in midweek.