Rafa Nadal is still uncertain when he can return to competitive tennis after withdrawing from this month’s ATP event in Barcelona as he recovers from a rib injury, his team told Reuters on Tuesday. The Spaniard, who has won 21 Grand Slam singles titles, was ruled out last month for up to six weeks with a stress fracture in his rib. The 35-year-old has withdrawn from this month’s Barcelona Open. “Rafa has just been withdrawn from the entry list in Barcelona,” the team said in a statement sent to Reuters. “We don’t know yet when he will be at his first tournament on clay this year. Hopefully, soon.” Nadal complained of a chest issue during his run to the final of the ATP 1000 event in Indian Wells, California last month. Tests in Barcelona revealed “a stress fracture of the third left costal arch”. Madrid and Rome host ATP Masters …