Leinster scrum-half Luke McGrath's set for a scan to assess the extent of his knee injury, after he was forced off during Saturday's win over the Scarlets.

The six-times capped Ireland number nine limped off just eight minutes into the second-half at the RDS and he's a major doubt for Saturday's Six Nations match against Wales. 

The injury is more likely to be felt by his province, however, should the issue cause the 25-year-old to be sidelined for more a few weeks. 

It could force head-coach Leo Cullen to leave either in-form winger James Lowe or second-row Scott Fardy out of the squad to face Saracens in the quarter-finals of the Champions Cup, as Jamison Gibson-Park would likely take up one of the two permitted slots for overseas players. 

Former Ireland back-row Alan Quinlan thinks it would create a difficult selection head-ache for Leinster head-coach Leo Cullen. 

"If Luke McGrath is out then Gibson-Park will have to come into the match-day 23 so you have to leave either Fardy or Lowe out. 

"James Lowe was outstanding on Saturday and he's been a superb signing for Leinster. 

Leinster Head Coach Leo Cullen / INPHO/Byran Keane

Cullen said it was too early to make a call on how serious McGrath's knee problem is when he spoke after Saturday's game.

"We’ll see. I’m not sure. He has a bag of ice on it but he is moving around okay. He will get it scanned. He was due to go back into camp but we will make some assessments on what is best for his recovery."

Leinster have already lost Josh van Flier and Robbie Henshaw to injury during the Six Nations.