Argentina’s Juan Martin del Potro is hard at work trying to make a return to the ATP Tour.

The 2009 US Open champion has been sidelined with a serious knee injury since June 2019 but he is still eager to make a return to the tour.

Del Potro on Wednesday posted pictures on his Twitter account of him playing tennis without a knee brace.

“Training,” he wrote, with pictures accompanying the post.

Del Potro, 32, has undergone four surgeries to his right knee in the past two years. His career has been riddled by injuries as he’s also struggled with career-threatening wrist troubles.