Rory McIlroy believes former world No.1 Tiger Woods faces a "long road" to recovery after undergoing a third back operation in 19 months.
Woods, who turns 40 in December, is on bed rest after what was described as a "follow-up procedure" to his second microdiscectomy in the middle of September.
The 14-time major winner first went under the knife on March 31, 2014, forcing him to miss the Masters for the first time in his career. No timetable has been set for his return to action but he had already been ruled out until 2016.