Argentina's Juan Martin del Potro has claimed that he is playing some of the best tennis of his career.

The 25-year-old has won three titles so far this year and also reached the final of the Shanghai Masters yesterday afternoon, but he was eventually defeated in three sets by Novak Djokovic.

Reflecting on his recent performances, Del Potro has insisted that he is on better form now than when he was when he won the US Open in 2009.

"I couldn't win a Grand Slam [title] like I did in 2009, but I reached finals in the [ATP World Tour] Masters 1000s. I have already won three tournaments [and] I beat the top guys, which is fantastic for me," he told reporters.

"I think I'm playing even better than 2009 or 2008 or last year. That's important [and] a good thing for the future. I still have the same goal, which is [to] get closer to the top guys. If I still work like this, I hope I can be there one day."

Del Potro has also qualified for the World Tour Finals in London next month.