Evergreen lock and former Wales Captain, Llewellyn, replaced injured Warriors star, Brent Cockbain, during the narrow defeat to the World Champions at Twickenham last week and now takes a place in the starting line-up, with Cockbain failing to recover from an ankle sprain.
Ospreys back row, Jonathan Thomas, is the next of three changes, one positional, in departing Coach Steve Hansen's final Wales Test side. Thomas was another injury doubt after the England match with thigh and shoulder bruising and he has been replaced by Blues Captain, Martyn Williams. Finally, Captain Colin Charvis switches to blindside flanker to accommodate Williams on the open side.
"Gareth is one of the senior players in our squad and is expected to be a leader both on and off the field," said Hansen. "He has done this with increasing success over the last two years, he is someone who has been a great asset to his country and will continue to do so long after chooses to retire, as I believe he will make a very good coach.
"He has looked after himself through the years and has been a valuable source of experience to the youngsters in the squad, as well as making his own contributions through his performances."
The 35-year-old lock's career spans two centuries and three decades, includes seven appearances as Captain and five international tries, starting in April 1989 against New Zealand at Cardiff Arms Park.
"Martyn Williams brings a level of experience to the team along with Llewellyn and he is a natural replacement for Jonathan Thomas who has not recovered in time to be in contention for this match," added Hansen. "We are expecting a big defensive performance from Martyn along with his usual continuity game.
"We have bracketed Iestyn and Tom together and we will make a decision on who will fill the No.12 shirt later in the week. Whoever misses out will be unlucky as they have both been in good form."
Further changes come on the replacements bench with Warriors lock Robert Sidoli taking Llewellyn's place and Leeds back row Alix Popham filling the gap vacated by Williams. Shanklin or Harris should take up a place on the bench to cover the centre position.