The Blitzboks had an ideal opportunity to gain crucial HSBC World Rugby Sevens Series log points to move them closer to Samoa and Australia and into the top four, but the defeat to Argentina scuppered the opportunity.
“We let ourselves down with this game," said Soyizwapi, who is playing in his 50th tournament.
"We had everything to play for and could have gained much needed points, especially as both Samoa and Australia handed us that opportunity, but we did not take it. And we only have ourselves to blame.
“It is frustrating, we did so well against Fiji and USA and that gave us a very good opportunity to get some valuable points, but then we didn't sustain the effort against Argentina. I wish I can lay my finger on why, but I can’t to be honest.”
The Blitzboks can get redemption at 12h48 on Sunday when they face Australia in the fifth-place play-off. A win will get them closer to that final qualifying spot, most likely to be confirmed at the HSBC London Sevens next weekend.
In their quarter-final, Argentina showed why they are one of the top two teams in the 2023 HSBC World Rugby Sevens Series by capitalising on uncharacteristic errors by the Springbok Sevens team to win their quarter-final by 21-12 in Toulouse on Saturday evening.
The Blitzboks could not replicate the form that they showed earlier against Fiji and the USA and came up short against the Pumas, who raced to a 21-0 lead before James Murphy scored twice late in the match.
The South Africans struggled with their defence and discipline against a team that had sealed their Olympic Games qualification earlier on Saturday.
Earlier on Saturday, the Springbok Sevens outplayed USA 24-7 to finish second in Pool C at the HSBC France Sevens, scoring four tries to one in a match where the South Africans clearly found their groove on attack.
They opened the scoring in the first minute. From the first lineout in the match, the ball was worked wide and when recycled, Ronald Brown spotted a gap and ran 80 meters to score.
The USA came back strong when shrugged off a weak Shaun Williams tackle to score, with the conversion pushing the North Americans ahead at the break.
Dewald Human was yellow carded for a dangerous tackle, but the South African defence held firm for the remainder of the half.
The Blitzboks started the second half on the right note as Christie Grobbelaar sliced through the USA defence to score under the sticks.
Human converted and scored himself soon after a lovely Blitzbok attack, with Justin Geduld and Ryan Oosthuizen involved as well. Human converted for a 19-7 lead.
Geduld then made a clutch tackle to snuff out a dangerous USA attack before Williams held off two defenders to score in the corner.
South Africa 24 (5), USA 7 (7)
South Africa – Tries: Ronald Brown, Christie Grobbelaar, Dewald Human, Shaun Williams. Conversions: Human (2).
USA – Try: Malacci Esdale. Conversion: Steve Tomasin.
South Africa 12 (0), Argentina 21 (7)
South Africa – Tries: James Murphy (2). Conversion: Justin Geduld.
Argentina – Tries: Marcos Moneta (2), Luciano Gonzalez. Conversions: Santiago Vera Feld (3).