Were McNabney to be called upon, it would cap a remarkable ascent for the 23-year-old, who has started just one game for Ulster this season after recovering from the anterior cruciate ligament injury that forced him to miss the entire 2025-26 campaign.
McNabney is one of four Ulster players on the bench alongside hooker Tom Stewart, prop Tom O’Toole and centre McCloskey, who drops out of the starting line-up for the first time in 2026.
With back-to-back world champions South Africa bringing their much-vaunted scrum power to Dublin next week, Farrell has opted to stick with first-choice props Andrew Porter and Tadhg Furlong.
Behind an experienced second row of Ryan and Beirne, Ryan Baird is retained after impressing on his return against Argentina while Timoney is entrusted with a first Test start at number eight after an eye-catching showing at open-side last week.
Back-up lock Darragh Murray is in line to win his fourth cap off the bench.
With Keenan not included, Hansen returns to the full-back jersey. The 28-year-old scored a hat-trick of tries on his first start at 15 against Australia last year.
Tommy O’Brien returns to left wing while Aki – a late withdrawal from the Argentina game because of illness – and Osborne represent a new centre partnership.
Gibson-Park returns at scrum-half after Craig Casey was preferred last week, while Prendergast is retained at fly-half with Ciaran Frawley kept in reserve.