Wales captain Alun Wyn Jones will make a world record 149th international appearance when he leads his country against Scotland.
England, Ireland and France all head into the final round of Six Nations matches in contention to be crowned champions.
New Zealand can clinch the Bledisloe Cup with a win on Saturday, but the trophy pursuit could yet go down to a fourth game in Brisbane.
The Rugby Football Union has charged 13 Barbarians players for breaching COVID-19 protocols which meant a match with England was cancelled.
Ben Youngs and Jamie George will win their 100th and 50th caps respectively when England take on Italy in their final Six Nations game.
Wales will wear black armbands in their Six Nations clash with Scotland to mark the passing of JJ Williams, a star of the 1970s.
Teddy Thomas is out of France's Six Nations clash with Ireland, so Gael Fickou will shift to the wing as Arthur Vincent returns to the XV.
Ben Youngs and Jamie George will achieve milestones for England in Saturday's Six Nations tussle with Italy in Rome.
Richie McCaw's 148 Test caps will be surpassed by Alun Wyn Jones when Wales take on Scotland in Llanelli on Saturday.
Sam Whitelock is back for the All Blacks ahead of Saturday's clash against the Wallabies.