There have been a number of notable wins since Townsend took over from Vern Cotter last June, with the thrilling Calcutta Cup triumph over England in February top of the list.
Additionally, there have been home and away successes over Australia, a home win over France and record win in Argentina. A rousing performance and narrow loss to the All Blacks could also be put in the highs column.
However, Townsend believes a win over the South Africans, given their current form, would be the best yet.
“Given what they have done recently, it would probably be our biggest win in the last couple of years,” said the coach.
“Obviously England stands out as such a memorable win. The fact they had won so many games in succession and that trophy we play for makes it even more special.
“But I just feel that South Africa are in the top two or three teams in the world with the way they play against the best teams in the world.
“Going to New Zealand and beating them, almost beating them a second time, showing what they were capable of last week against France as they came from behind to get a great win – that all shows they are going to be a tough team to beat.”
Townsend has made six personnel changes to the team that started the 54-17 win over Fiji, claiming that this weekend’s XV was “80 per cent” of how he thought it would be when he was mapping out the four-match series.
Glasgow centre Huw Jones is recalled at outside centre and gets a chance to put right a below-par showing in Cardiff at the start of the month against the nation he blossomed as a professional player with Western Province and Stormers.
That is the only change in the back division, but the pack has been reshuffled in preparation for what is likely to be a brutal contest with the most physical set of forwards in the game.
Stuart McInally returns at hooker, while Gordon Reid comes in at loosehead ahead of Allan Dell. It’s all change at lock, with Ben Toolis and Jonny Gray coming in and last week’s impressive debutant Sam Skinner dropping back to loosehead. Hamish Watson returns at openside.
There is no place in the 23 this week for Newcastle flanker Gary Graham, who joined the squad this week after opting for England without being capped at the start of the year.
Townsend was clear when asked if Saturday presented the most physical challenge in Test rugby.
“Yes. It’s number one,” he said. “We get physical challenges in the Six Nations with the likes of England and France and Ireland but any coach will tell you that the biggest physical challenge is South Africa. It always has been.
“They have evolved their game since Rassie [Erasmus] took over [as coach] but they’ve not gone away from the forward pack. They select the biggest and strongest men they can find.”
Townsend expressed confidence that centre Jones can recover from his blip in Wales and return to the heights of previous sparkling performances in a Scotland jersey.
“It’s a great game for him,” said the coach. “He played a few seasons in South Africa and he’ll know a few of their players. He is fresh. He trained last week and was decisive in training.
“When he played well last year a lot of that was to do with how he trained. He has been sharp and can’t wait to get on the ball.”
Scotland: Stuart Hogg (Glasgow); Tommy Seymour (Glasgow), Huw Jones (Glasgow), Pete Horne (Glasgow), Sean Maitland (Saracens); Finn Russell (Racing 92), Greig Laidlaw (c) (Clermont); Gordon Reid (London Irish), Stuart McInally (Edinburgh), Willem Nel (Edinburgh), Ben Toolis (Edinburgh), Jonny Gray (Glasgow), Sam Skinner (Exeter Chiefs), Hamish Watson (Edinburgh), Ryan Wilson (Glasgow). Replacements: Subs: Fraser Brown (Glasgow); Allan Dell (Edinburgh); Simon Berghan (Edinburgh); Josh Strauss (Sales Sharks); Jamie Ritchie (Edinburgh); Ali Price (Glasgow); Adam Hastings (Glasgow); Chris Harris (Newcastle).