Faf du Plessis was forced to concede West Indies were simply too good for South Africa as the Proteas' World Twenty20 hopes were dealt a huge blow.
The Windies secured a semi-final spot with a three-wicket win on Friday that proved a little more nervy than they may have anticipated after restricting the Proteas to 122-8.
Du Plessis saw his side battle manfully to stay in the contest until the Windies completed the job with two balls to spare, leaving South Africa on the brink of a likely exit.
"It felt like the whole game we were half a step behind West Indies and we were trying to catch up the whole time," the losing captain said.
"Ten runs maybe more from the batters [would have provided a different result]. But a great fight by the boys.
"This game makes us all very old, very quickly. West Indies were just a little bit better than us. It was a little bit frantic that first six overs."
The Proteas were 47-5 at one stage, Du Plessis himself going cheaply for nine, with only Quinton de Kock (47) and David Wiese (28) providing any serious resistance.
Victorious Windies captain Darren Sammy added: "We came here to win this match and qualify and we've done that, so we're really happy."
South Africa's fate rests at least in part on the result between England and Sri Lanka on Saturday, where a win for the former would definitely send Du Plessis' side out.