Ireland head coach Andy Farrell says he is confident in the return-to-play process after Calvin Nash was passed fit to play against Scotland in the Six Nations on Saturday.

Farrell says he passed his return-to-play protocols with "flying colours".

Munster's Nash, 26, was then cleared to play by an independent doctor on Thursday.

Farrell has named Nash in an unchanged Ireland team to face Scotland in a Six Nations title decider at Aviva Stadium.

He said: "I would understand that [concern] but if you're in the inner circle and you understand the process that these players have to go through now, you would thoroughly back that process.

"One, he has gone through it with flying colours and he never looked like failing for one second. And two, the process, I think, is very sound.

"Accumulating a few days of getting to the next stage, passing them with flying colours and having a conversation, an interview, a wellness type appointment with an independent doctor today, and there have been no issues there. So, all's good to go."

Nash was taken off following a collision with England's Tommy Freeman and failed his head injury assessment (HIA), meaning he could not return to the pitch.

However, Farrell said he passed every subsequent stage of the return-to-play process and trained fully on Wednesday.

"He passed the three stages he had to go to," added the Ireland coach.

"He trained fully yesterday without doing contact in the session but had to do contact after the session. Passed that flying colours, no problem whatsoever. He had to see an independent doctor, if it's a seven-day turnaround you have to do that and he passed that with flying colours as well."

When asked if he considered leaving Nash out despite him passing the protocols, Farrell added: "You've got to trust the process and what you've been told and what you're seeing daily as well.

"We've got experts in that field who have been through a lot in this regard in the last few years themselves, so you trust the experts on this."

Farrell also clarified that Ciaran Frawley is required to go through a 12-day return-to-play programme as opposed to Nash's seven-day protocols.

Leinster full-back Frawley has returned to his club after he was forced off in the second half against England, having replaced Nash.