(CNN) -- Rafael Nadal admitted his knee injury continues to "bother" him after the Spaniard suffered double defeat in the final of the singles and doubles tournaments at the VTR Open in Vina del Mar, Chile.
The clay court event was the former world No. 1's first tournament in seven months due to an injury to his left knee, which caused him to miss both the U.S. Open as well as the Australian Open.
"The knee is still bothering me, but you have to face adversity with the best possible face and look forward to keep working and enjoy what I like the most, to play tennis," said the 11-time grand slam champion told the ATP World Tour's website.
Despite his discomfort and a 6-7 (2-7) 7-6 (8-6) 6-4 loss to Argentina's Horacio Zeballos, Nadal stressed the positives he had taken away from the event having played nine matches in six days.
"A week ago we didn't know how the body would respond," the 26-year-old Mallorcan. "[Now] at least I know we can compete at a certain level.
"I think that was a positive week... I will try to keep improving my physical sensations day-by-day, which is the most important thing because I don't feel that my tennis level is bad. I need more time on court.
World No. 43 Zeballos picked up his first career Tour title and became just the third player to beat Nadal in a clay court final, following in the foot steps of Roger Federer and Novak Djokovic.
It was only Nadal's fifth defeat in 41 clay court finals.
"The tennis is important, but for me the best thing was to have the feelings I've had this week, with a full stadium and one of the best crowds I've ever had in my life," added Nadal. "It's a place I won't forget because of the love people gave me.
"I was two points away from winning the title, but I said from first day that the result was not the most important thing, although I would've liked to win.
"My opponent won, he deserved it and I congratulate him. Still, to win four matches in a row is good news for me."
Nadal and Argentine partner Juan Monaco lost the doubles final to Italians Potito Starace and Paolo Lorenzi.
This week Nadal will continue his rehabilitation in South America, where he will be top seed at this week's Brazil Open in Sao Paulo.