Rafael Nadal says he is nervous about his return to tennis after a seven-month layoff and believes it may be some time before his injured knee is completely healed.

Nadal told Canal Plus television Friday that "I'm prepared to accept that my knee may not respond well at the beginning." He has considered playing off and on during the first three months of 2013.

The 26-year-old Spaniard is set to play in Abu Dhabi on Dec. 27. It will be his first match since he was sidelined with tendinitis in his left knee after a second-round loss to 100th-ranked Lukas Rosol at Wimbledon in June.

Nadal says his goal is to be back in top form for Monte Carlo in April.