Germany will meet Argentina in Sunday's final at the Maracana, having brutally swept aside hosts Brazil 7-1 on Tuesday.
Mertesacker helped maintain Germany's defensive solidity when he was introduced at half-time - allowing the likes of Thomas Muller, Mesut Ozil and Andre Schurrle to wreak havoc further up the field.
Ozil is one of a host of players who have graduated from the successful under-21 side of 2009 to the current first team, along with Manuel Neuer, Jerome Boateng, Sami Khedira and Mats Hummels, with Mertesacker claiming a final appearance in Brazil has come about through years of hard work.
"It started off in 2009 when we won the under-21 tournament (UEFA European Championship) and beat England 4-0. I think there's a small link between these two tournaments," he explained.
"The 2009 tournament was a real turning point. The youth academies started developing well over the last five or six years."
Germany and Argentina are set to do battle for a third successive World Cup, with the former having triumphed in 2006 and 2010.
Mertesacker feels coach Low has greater depth at his disposal this time around.
"We have one of the strongest squads I've ever played in," he added.
"We have two excellent players for every position and everyone believes in each other.
"We have created excellent team spirit during the tournament and with those magnificent players growing up together it makes it easier."
