On Friday, the 29-year-old defender posted the following picture on social networking site Twitter.
It is an interesting message from Mertesacker, who speaks about his perspective having slightly changed over the last 24 or so years but his emotions remaining the same.
Back in 1990, Mertesacker enjoyed watching his country Germany win the World Cup. The tournament was held in Italy that year, and the final was between Die Mannschaft and Argentina.
Germany won that contest 1-0 at the Stadio Olimpico in Rome, thanks to a penalty from Andreas Brehme in the 85th minute.
On Sunday, Germany will take on the same opponents in the final of the 2014 World Cup final at the Maracana in Rio de Janeiro.
The similarities between the final in 1990 and the one that will be played on Sunday are hard to miss. Both stadiums are iconic, most cities are hugely popular and both teams are footballing giants. Then Argentina had Diego Maradona, now they have Lionel Messi.
Mertesacker watched his country win the World Cup as a child and now he is on the verge of achieving the feat as a footballer.
It is a dream of all football fans.