Bundee Aki is in line to make his Ireland debut against South Africa but Tommy O'Donnell is struggling with a shoulder injury.
Connacht record a fourth successive win by beating the Cheetahs 23-15 in the Pro14 at the Sportsground in Galway.
Connacht end a run of four straight Pro14 defeats as they edge out out 14-man Munster in a tense game in Galway.
Connacht make it two wins from two in the Challenge Cup as Worcester lose their ninth away game in a row in the tournament at the Sportsground.
Audio & Video
Ulster back Tommy Bowe hopes the team can bounce back from the weekend defeat at Zebre by beating Irish rivals Connacht at Kingspan Stadium on Friday night.
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