AP McCoy 's teammate burns retired from Scottish competitive National . Paul Nicholls pulls out due to unsuitable drying conditions at Ayr . McCoy is due to retire next year after over 4,000 career starts .
AP McCoy 's mount Benvolio withdrawn from Scottish Grand National . Paul Nicholls pulls horse due to unsuitable drying conditions at Ayr . McCoy is due to retire next week after over 4,000 career wins .