New concussion setback for Sexton
Given Sexton's history of concussion, Ireland coach Joe Schmidt will be sweating over his fitness ahead the Six Nations opener against Wales in Dublin on February 7.
He was forced to take a 12-week break from the game after his then French club, Racing Metro, confirmed that Sexton had suffered four concussions in 2014.
He returned to the game during the 2015 Six Nations tournament, but his latest setback will leave Schmidt sweating – as the flyhalf faces a series of 'return to play protocols'.
Sexton was injured when he clashed heads with former Leinster teammate Brendan Macken.
On his 100th Leinster appearance, and captaining the side in the absence of Isa Nacewa despite the return of Jamie Heaslip (from concussion), Sexton lasted just eight minutes of this team's record 10-51 loss to Wasps in a European Champions Cup match at the weekend.
Sexton is now under the care of the Ireland medical team, ahead of next week's opening round of the Six Nations.
"Johnny got just a head knock," Leinster coach Leo Cullen said.
"We didn't want to risk him going back out there – so he'll follow the usual return to play protocols.
"Those guys are in [Ireland] camp this week, but he looked okay in the dressing room [after the game]."
The 30-year-old will train away from the rest of the Ireland squad for the first few days, as they gather at Carton House on Monday.
Meanwhile, prop Marty Moore, who was named in Schmidt's 35-man squad for the first two Six Nations games against Wales and France, limped out of Leinster's match with a hamstring injury.
Sources: Irish Times & RTE Sport
