When Tim Wakefield was pitching, every fifth day was Knuckleball Day. But then he retired, and the 200-game winner was replaced in the Red Sox rotation by a bunch of guys who couldn’t get anyone out. Tuesday, Wake was back, but, sadly, not to pitch. He was in town for the premiere of the new documentary “Knuckleball!,” and Mayor Tom Menino marked the occasion by declaring it Knuckleball Day in Boston. The film, by directors Ricki Stern and Annie Sundberg, is all about the strangely slow and stealth pitch known as the knuckleball, and it focuses on the unorthodox careers of Wakefield, Mets pitcher R.A. Dickey , and the great Phil Niekro . Wake was joined at the screening by Niekro, Wilbur Wood , and Charlie Hough . Asked how they’d do as a rotation, Wakefield replied: “We’d win more than we lost.” After the screening, Wakefield answered a few questions from the audience and then headed over to Fenway for an afterparty.