Marais gets pivotal role for Cheetahs
Marais' move to flyhalf sees Fred Zeilinga drop down to the bench. Clinton Swart will be wearing the No.12 jersey.
In the pack, Carl Wegner will be running onto the field in his 50th match for the Cheetahs.
He will be replacing the injured Justin Basson. Rynier Bernardo will be providing cover on the bench.
In their previous encounter, Cardiff Blues beat the Toyota Cheetahs 25-20 at Arms Park in Round 14.
"The players understand the importance of this game and have prepared as best possible. Cardiff Blues is a decent outfit and we are in for a tough battle," said Cheetahs coach Rory Duncan.
Cheetahs: 15 Clayton Blommetjies, 14 William Small-Smith, 13 Francois Venter (captain), 12 Clinton Swart, 11 Sibhale Maxane, 10 Niel Marais, 9 Tian Meyer, 8 Uzair Cassiem, 7 Teboho Mohoje, 6 Paul Schoeman, 5 Reniel Hugo, 4 Carl Wegner, 3 Johan Coetzee, 2 Torsten van Jaarsveld, 1 Retshegofaditswe Nche.
Replacements: 16 Jacques du Toit, 17 Erich de Jager, 18 Tom Botha, 19 Rynier Bernardo, 20 Henco Venter, 21 Mthokozisi Mkhabela, 22 Fred Zeilinga, 23 Adriaan Coertzen.
Cardiff Blues: 15 Matthew Morgan, 14 Alex Cuthbert, 13 Garyn Smith, 12 Willis Halaholo, 11 Owen Lane, 10 Gareth Anscombe (captain), 9 Lloyd Williams, 8 Josh Navidi, 7 Olly Robinson, 6 Macauley Cook, 5 Damian Welch, 4 Seb Davies, 3 Anton Peikrishvili, 2 Kirby Myhill, 1 Rhys Gill.
Replacements: 16 Ethan Lewis, 17 Brad Thyer, 18 Dillon Lewis, 19 Josh Turnbull, 20 Ellis Jenkins, 21 Tomos Williams, 22 Steven Shingler, 23 Rey Lee-Lo.
Date: Saturday, April 7
Venue: Free State Stadium, Bloemfontein
Kick-off: 15.00 (14.00 UK & Ireland time; 13.00 GMT)
Referee: Mike Adamson (Scotland)
Assistant referees: Sean Gallagher (Ireland), Ben Crouse (South Africa)
TMO: Johan Greeff (South Africa)