Rafael Nadal has said he is worried how his healed knee would react after he makes his long-awaited comeback in the upcoming exhibition tournament in Abu Dhabi on December 27 following a seven-month hiatus.

Nadal admitted it might take him some time to return in top form, but added that he trusted his medical staff, Stuff.co.nz reports.

The 26-year-old Spaniard is set to play an exhibition tournament in Abu Dhabi on December 27, his first action since being sidelined with tendinitis in his left knee following a second-round loss to then 100th-ranked Lukas Rosol at Wimbledon in June.