As many as 110 ATP world ranking points - not to mention the winners' prize of approximately R85 000 - will be at stake in the Soweto tournament and winning the third edition of the Soweto Open would elevate Van der Merwe or De Voest to a potential best-ever world ranking position.
De Voest, in particular, has an inviting opportunity to improve his current 185th world ranking by as many as 50 places because Van der Merwe was a finalist last year and would therefore have less chance to add to his current world points tally.
It will not be an easy undertaking for the fourth and sixth seeded South African Davis Cup pair in the face of a substantial and varied overseas challenge headed by Jamaican-born, German Dustin Brown, the defending champion and No 1 seed for this year's event.
It could hardly have been more daunting for budding South African stars Nikala Scholz and Chanel Simmonds when the draws for the men's and women's events were made on Saturday.
Scholtz, the son of former Western Province rugby hero, Kala Scholtz, whom many consider the most promising young male player in the country, finds himself paired with Brown in the first round.
The 18 year-old Simmonds, who made a striking impact in this tournament last year, faces Russia's defending champion and third seed Nina Bratchikova in the opening round of the women's singles.
Out of the women's singles draw were Alberta Brianti of Italy and Thailand's Tamarine Tanasugain, who had been the tentative first and second seeds respectively, with officials unaware of the reasons for their late withdrawal.
The draw also means there will be no repeat of last year's men's singles final between Brown and Van der Merwe, with both placed in the same half of he draw and earmarked for a semifinal match-up.
Van der Merwe, who reversed his defeat against Brown on the way to a creditable semifinal berth in this year's South African Open at Montecasino, is seeded behind three of the overseas contingent.
An intriguing match-up in the opening round is the match between South African Davis Cup teammates De Voest and Raven Klaasen, with De Voest favoured as the sixth seed and Klaasen having received a wild card entry.