Grey’s Anatomy star Kevin McKidd has addressed speculation that he has been cast to play Arthur Weasley in HBO’s highly anticipated Harry Potter TV series . Rumors about McKidd’s potential casting recently surfaced when eagle-eyed fans noticed that Gracie Cochrane, the young actor set to play Ginny Weasley in the forthcoming adaptation, started following the Scottish actor on Instagram. Asked about the growing online chatter in a new interview with Entertainment Weekly , McKidd, 52, who on Thursday departed the long-running medical drama after 18 years as Dr. Owen Hunt , answered coyly. “I saw something about this,” he said. “And listen, I would never say never. I’m a massive Harry Potter fan.” He revealed that years ago, when he was starring in the short-lived sci-fi series Journeymen , Harry Potter director David Yates sent him a letter, offering him a role in the final two films: 2010’s Deathly Hallows — Part 1 and Part 2 (2011).…