Rashid Khan and Travis Head may also return to Hove, news which comes amid a difficult start to the off-season for the club amid Jason Gillespie's departure
Sussex have confirmed Stiaan van Zyl as an overseas player for the 2021 season.
The club also remain hopeful of Travis Head completing his move to Hove, while Rashid Khan is due to return.
South African Van Zyl was unable to return to Hove for this season due to quarantine restrictions upon re-entry to the United Kingdom, enforced due to the ongoing COVID-19 pandemic.
Though his Kolpak deal will be cancelled, Sussex have announced the 33-year-old will be one of their foreign signings for the new campaign.
Following the end of Kolpak contracts counties are now permitted to acquired two overseas players for the County Championship and One-day Cup. Two are already permitted in the T20 Blast.
Van Zyl moved to Sussex in 2017 and has since scored 2,630 runs and taken 14 wickets across all formats.
He could be joined by Australia batsman Head, whose deal to move to Sussex was delayed due to the pandemic.
Rashid Khan could return for a third season at Hove in 2021
Rashid was also unable to feature in a third season in the Blast due to the competition clashing with the Caribbean Premier League and Indian Premier League.
Should the Afghanistan skipper fill one overseas player birth for the Blast, it is hoped David Wiese will join him despite biding farewell to the club earlier this week.
Wiese, like fellow-countryman Van Zyl, was on a Kolpak deal but Sussex have not yet moved him onto an overseas deal.
The club are hopeful of enlisting him for the 20-over tournament to extend his spell on the south coast to a fifth season.
It is hoped the quartet will all feature for Sussex in 2021 and help offset the departure of coach Jason Gillespie as well as Danny Briggs, Harry Finch and Luke Wells.
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