Had Australia won, they would have faced fourth-placed New Zealand in the first semi-final at Old Trafford on Tuesday.
Reigning champions Australia have already qualified for the semi-finals, while South Africa cannot make it through to the last four.
Saturday's World Cup match against reigning champions Australia is set to be Tahir's 107th and last ODI before the leg-spinner bows out of the 50-over game at international level.
In the first World Cup game at Lord's, Pakistan won the toss and put up a good total.
The South African team has lurched from defeat to defeat, their weaknesses clearly visible.
Tahir has been South Africa’s strike bowler in recent times and captain Faf du Plessis went on record to mention that the veteran has been responsible for the Proteas’ ascent
Tahir has been South Africa’s strike bowler in recent times and captain Faf du Plessis went on record to mention that the veteran has been responsible for the Proteas’ ascent.
Quinton de Kock scored 68 for South Africa as they coasted home in the 28th over.
Tahir ended with figures of four for 29 in his seven overs, while Morris returned with exquisite numbers of three for 13 in his 6.1 overs.
South Africa are in desperate need of a victory on Wednesday after their two defeats.