Having arrived in Brazil as his country's first-choice forward, he watched the entire semi-final from the bench having been dropped earlier in the tournament and replaced by Klose. (Agencies)
Goetze was again among the substitutes for Sunday's final and would have had few expectations of being involved as coach Joachim Loew understandably kept faith with the team that had marched into the final in such style.
However, Loew threw him on for Klose two minutes from the end of normal time and Goetze repaid him in the most spectacular way possible, smashing home a brilliant goal seven minutes from the end of extra time.
The goal gave Germany a 1-0 win over Argentina and secured his country's fourth World Cup and first since 1990 - two years before he was born.
Fellow substitute Andre Schuerrle advanced past a tiring Argentine defence down the left and picked out Goetze in the box.
The 22-year-old leapt to control the ball on his chest before stretching to sweep a sweet volley beyond Sergio Romero.
A few months ago Goetze's career seemed to be on an unstoppable upward trajectory.
Having helped Borussia Dortmund to two Bundesliga titles and into the 2013 Champions League final, he did what all great German players seem to do - agree a huge transfer to Bayern Munich.
Another league and cup double duly followed and he completely won over Loew, who loved the versatility that allowed him to use the quick-footed and mobile player as a midfielder or even a lone striker.
Grasped the opportunity
Once in Brazil, he started Germany's opening 4-0 win over Portugal and got the first goal in a 2-2 draw with Ghana but was a substitute in the final group game against the United States.
He was restored to the starting lineup for the second round against Algeria but played poorly and was hauled off at halftime.
With Klose established in the side, he had to settle for another late substitute appearance in the quarter-final victory over France and must have found it difficult as pundits praised Loew for finally finding the right lineup.
How Goetze must have longed to be involved as Brazil's defence opened up so invitingly in Belo Horizonte.
But the goals were spread elsewhere and it was Klose, supported by Thomas Mueller and Tony Kroos, who were again going to be the goalscoring threat in the final.
Loew's plans for Sunday's final were no doubt disrupted by the pre-match withdrawal of Sami Khedira and then being forced to replace his replacement, Christoph Kramer with Schuerrle after half an hour.
But there was still time for Goetze to become involved and he grasped the opportunity, becoming the only substitute to score the winning goal in a World Cup final.
"I've got to thank my family and friends who believed in me," said Goetze.
"Yes there were some other players who came to me and said, 'You'll do it tonight'. The ball was just there and then it was in. It was deliverance for the team and it's a great feeling to have been able to make a contribution to that,” he added.
Klose underlined the team spirit that kept things positive when both men were spending time on the bench.
"It's incredibly important that we stuck together," he said.
"At halftime I told Mario 'I think you'll get a goal tonight.' It's just incredible,” he added.
Loew too felt that Goetze's time had come
"I had the feeling that he could do something decisive today because Mario is the kind of player who can decide matches," he said.
"I had a feeling somehow that he could bring this thing to a conclusion,” he added
Having arrived in Brazil as his country's first-choice forward, he watched the entire semi-final from the bench having been dropped earlier in the tournament and replaced by Klose.