World Rugby's proposed changed to the international calendar have not gone down well with top players.
Mark McCall hailed Schalk Burger as "one of rugby's truly great players" after the back-row decided to return to South Africa.
Cory Hill was injured while scoring a try which set Wales on their way to beating England in Cardiff and will not face Scotland or Ireland.
Mathew Tait, who made his England debut at the age of 18, has called time on his career on medical advice.
Tolu Latu will not play Super Rugby until April after the Waratahs hooker was banned for six weeks.
A pectoral tear sustained against the Stormers on Saturday is set to rule Lions captain Warren Whiteley out of action for up to eight weeks.
Maro Itoje may return quicker than expected for England after Courtney Lawes was ruled out of the rest of the Six Nations.
Courtney Lawes will be sidelined for at least four weeks, ruling him out of England's Six Nations clashes with Italy and Scotland.
Lyon claimed a third successive win and are breathing down Clermont's necks after beating them at Matmut Stade de Gerland,
Conor O'Shea says Italy are making progress and there is a belief in the camp that they can turn the corner despite defeat to Ireland.