United, who won the competition under Jose Mourinho in 2017, travel to Bruges for the first leg on 20 February before returning to Old Trafford a week later.
Henry Davids scored an unbeaten 77 runs to help Paarl Rocks win the second edition of the Mzansi Super League by eight wickets over the Tshwane Spartans at Boland Park, Paarl on Monday.
The Blitzboks came to the match with high spirit and confidence after winning all their matches from day one and two respectively.
The victory has taken the home side the final spot later on Sunday between Fiji and New Zealand.
New Zealand have been crowned Cape Town Sevens champions after beating the Blitzboks 7-5 at Cape Town Stadium on Sunday.
Cricket South Africa has on Saturday announced the appointment of Mark Boucher as Proteas head coach and Enoch Nkwe as an assistant coach.
Springbok Sevens secure a quarterfinal spot following a 26-14 victory over Fiji on Saturday at Cape Town Stadium on the day two of the Cape Town Sevens.
Jose Mourinho said he needed time but the squad had the 'talent and desire' to improve.
The league will be a strength versus strength domestic competition, designed to raise the standard of South African domestic cricket and give provincial players the chance to measure their skills against the established Proteas, most of whom will be taking part.
The Blitzboks powered to a 49-0 win over Japan in their HSBC World Rugby Sevens Series opener at the Cape Town Stadium on Friday.
