Table-toppers Ospreys host Connacht on Friday looking to make it seven wins on the bounce in the Guinness PRO12.
Saturday sees four European Rugby Challenge Cup showdowns, with Cardiff, Exeter, Connacht and Gloucester all in action.
Nathan White will make his Ireland debut against South Africa should Mike Ross fail to shake off a groin injury.
Cardiff Blues kicked off their European Rugby Challenge Cup campaign with a 37-14 bonus-point victory over Grenoble.
There are seven European Rugby Challenge Cup matches across Saturday and Sunday. Sky Sports previews them all.
Connacht got their Pro12 campaign back on track as Craig Ronaldson kicked three penalties in a 9-6 win over Treviso.
Sam Hobbs scored a controversial late try as Cardiff recovered from a 14-point deficit to draw 24-24 at Connacht.
Early leaders Ospreys travel to Italy to take on Zebre, who are looking to make it two wins on the bounce.
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