Perfect made his next title defense against Big Boss Man at WrestleMania VII , where he retained the title by losing via disqualification after the challenger was attacked by Haku and The Barbarian .   The following month, Perfect won a battle royal on the April 27 episode of Saturday Night's Main Event by last eliminating Greg Valentine ,   which lead to a match between the two for Perfect's title on the May 14 episode of Prime Time Wrestling , where Perfect retained the title via disqualification.  On the June 15 episode of Superstars , Bobby Heenan retired as a manager and introduced The Coach as Hennig's new manager. Hennig began a rivalry with British Bulldog but he suffered a back injury, which lead to the rivalry being wrapped up and Bret Hart being announced as his next challenger on the July 13 episode of Superstars . Perfect lost the title to Hart at SummerSlam   and a broken tailbone and buldged discs forced him to retire from the ring.