Johnny Sexton ruled out of Leinster's crucial Champions Cup clash against Toulouse
Leinster will need to put on their best performance of the season without Jonathan Sexton to put Toulouse to the sword in the Champions Cup on Saturday (KO1.0, BT Sport 2).
The minor calf problem caused to the World Player of the Year is just too vulnerable to more serious trouble should the out-half receive a bang to it.
For instance, a Grade-1 calf strain takes seven to 10 days to heal, whereas a Grade-2 strain expands the rehabilitation process to our-six weeks.
The close proximity of the Six Nations may, or may not, have been a consideration in Leo Cullen's decision to turn to Ross Byrne.
No doubt, it will come as a shot in the arm to the French league leaders as they look to truly announce their intentions to succeed Leinster as European champions.
The race for that fifth star is on and Toulouse are a lot closer than they looked last season.
Sexton has been a scourge to the French in recent years, most recently orchestrating and finishing off that 45-metre drop goal at Stade de France last February.
The removal of the centrepiece to Leinster's game plan is a big blow.