Rory McIlroy will turn professional after the Walker Cup

The home team for the 8-9 September event were at the Royal County Down course in Newcastle, Northern Ireland, to get a feel for the venue.

But McIlroy was forced to spectate and could miss Wednesday's play as well.

"It is a matter of rest and exercises and hopefully it will be all right by the end of the week," said McIlroy.

"I was playing in Donegal at the weekend and in the practice round on Friday I was trying to play a ball out of the rough.

"As soon as I hit it I felt something go in my back and went to the physio.

"I have sprained one of the joints that holds the last two vertebrae in my back."

McIlroy hopes to play with his Walker Cup team-mates on Thursday as the warm-up continues to what will be his last event as an amateur.

"To play it at home in front of my friends and family is going to be special for me.

"But it is going to be great for everyone in the team."