After losing to Pakistan in their previous match, Namibia was forced to make two changes to their lineup, with Karl Birkenstock and Bernard Scholtz replacing Jan Frylinck and Ben Shikongo.
Ireland, which lost their last encounter with Sri Lanka, made no changes to their lineup for this crucial match.
Williamson faced Australia in a warm-up match prior to the ICC Men's T20 World Cup Super-12s. He led New Zealand in scoring with 37 off 30 balls while also aggravating his elbow.
