"I thought they were just being funny, and then I realized there was a meaning behind it," said Kunkle-Miller, a certified sports psychologist who has been practicing in Mt. Lebanon for 12 years.
It means the Pirates are winning and the players and their fans are having fun. It became prominent among the players in May after catcher Rod Barajas belted a game-winning home run against the Washington Nationals at PNC Park. As he rounded third, he found his teammates waiting for him at home plate, each one displaying the "Z."
"We just started doing it, we've been raking ever since," said starter A.J. Burnett. "That was my favorite part of the night, seeing 20 guys behind home plate doing that. It shows you what a group we have."
"It gives them a sense of shared goal and that positive message of winning. It unifies them," said Kunkle-Miller. "I remember when the Pirates were in the World Series (in 1979), they would play 'We Are Family' to rally the fans and get everybody going. This is a variation on that."
Like playoff beards, the Green Weenie and the Terrible Towel.
"Athletes in general like to be part of a team," said Aimee Kimball, director of mental training at UPMC Sports Medicine on Pittsburgh's South Side. "So something that they all have in common, like an inside joke, bonds them a little more. And the fans then take it to another level."
"I love it because it's specific to them," said Pirates fan James Hans, 30, of Delmar, who attended Tuesday night's game at PNC Park. "They're a band of brothers sticking together."