Melbourne, Jan 29 (DPA) His ranking may be set for a fall to fourth in the world on Monday, but Rafael Nadal has more pressing matters on his mind after his return to Spain for tests on his injured right knee.

The defending champion, who lost to Andy Murray in the Australian Open quarter-finals – he quit with knee troubles in the third set – voiced optimism upon his return to Barcelona that he would be able to recover quickly.

Opinions from the Nadal camp appear to be mixed on the prognosis, with a scan conducted Thursday and an examination by Spanish federation doctor Angel Ruiz Cotorro expected to more precisely diagnose the problem.

In Spain, Nadal sounded optimistic: “I’m not worried. It’ just a small niggle. I hope to recover in a week.”

The one-time world number one said that the complaint was similar to the injury that struck him last year in the third round of the French Open, contributing to his loss to Robin Soderling and an inability to play at Wimbledon and defend his 2008 title.