Johnny Sexton has been ruled out of Leinster's Heineken Champions Cup meeting with the Northampton Saints this Saturday, but the province will send him for a further scan before determining the extent of his knee injury.

The outhalf suffered the knock during Leinster's bonus point win away to the Saints on Saturday, falling awkwardly after passing to Jordan Larmour in the lead up to their fourth try.

The province say Sexton has had a scan on the injury, but the extent of the damage is yet to be determined, with a further examination to take place this week.

The 34-year-old faces a race against time to be fit for the start of the Six Nations, with Ireland to begin life under Andy Farrell against Scotland at the Aviva Stadium on Saturday February 1st.

The province could also be without influential second-row James Ryan for the return fixture against the Premiership leaders on Saturday. He is following the return to play protocols after suffering a head injury during the second half at Franklin's Gardens.

In a further blow, centre Joe Tomane is facing up to two months on the sidelines. The Australia international has suffered a recurrence of the hamstring injury he picked up in November, and is set to be absent for between six and eight weeks.

In better news, hooker Sean Cronin could make his first appearance since the World Cup this weekend. The hooker - who missed the quarter-final of the tournament due to a neck injury, has resumed full training.

Leinster are in pole position to secure a home quarter-final following Saturday's seven-try rout of the Saints.

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