ROME (AP) — Novak Djokovic’s performance was so poor on Sunday that even the 24-time Grand Slam champion admitted it was “concerning.” Djokovic put on one of his worst displays at one of his favorite tournaments as he was upset by 29th-seeded Alejandro Tabilo in the third round of the Italian Open. It was Djokovic’s first match since accidentally getting knocked on the head by a water bottle while signing autographs after his opening win on Friday. “I managed to sleep okay. I had headaches. The next day or yesterday was pretty fine, so I thought it’s okay. Maybe it is okay. Maybe it’s not,” Djokovic said. “I mean, the way I felt on the court today was just completely like a different player entered into my shoes. Just no rhythm, no tempo, no balance whatsoever on any shot. It’s a bit concerning.” Djokovic started off with a double-fault and it didn’t get much better for the six-time Rome champion.