It's been a long slog for Harmer. He was part of the national setup in 2015 but failed to get the desired returns. Harmer did pick up ten wickets in the tour of India that year, but conceded too many runs as the Proteas went down 2-0 in the Test series.
After being looked off, Harmer signed a Kolpak deal with Essex in 2017, effectively ending his chances of a return. But eight years and hundreds of wickets later, Harmer found himself back on Indian soil with ball in hand.
The Pretoria native proceeded to take 17 scalps at a scarcely believable average of 8.94 as the Proteas romped to a historic 2-0 clean sweep. Harmer's efforts earned him the Man of the Series accolade.
"It's been a long road," the 36-year-old told ESPN.
"Ten years later, back here, completely different feelings. I'm going to leave with a lot more fond memories than I did the last time but I think as a whole, as a team, for us to leave here 2-0, that was always the goal. And for us to get over the line against a very good Indian team, I think it was a hell of an effort."
But Harmer knows his place. Proteas premier all-format spinner Keshav Maharaj was also in the squad and while he outperformed him, Harmer understands his role.
"Keshav's record speaks for itself," he continued.
"He's an incredible bowler and he deserves to be the number one spinner. I'm very happy playing the supporting role and if the opportunity presents itself for me to play, I try and take it with both hands. At the end of the day, I just need to make sure that I'm getting better, keep trying to evolve, keep trying to get better."
Proteas strike bowler Kagiso Rabada missed the series due to a rib injury, forcing Harmer and Maharaj to pick up the load. Captain Temba Bavuma heaped praise on Harmer for stepping up when the team needed it most.
"Simon was the man for us in this series," said the diminutive leader.
"We're so used to Kesh being that guy. We're in a good space from a bowling point of view. A guy like Simon, Kesh as well on his days, them stepping up, having lost a guy like KG who was a big player for us, again speaks about the need for the guys to want to do it for the team."