The Raptors coach would like to know, however, what exactly "it" is.
"One thing, everybody's got their opinion, if he feels that way about us or whoever else, you've got to go out in this league to prove to people, if they don't feel we have 'it,'" Casey said prior to Toronto's regular-season finale against Charlotte on Wednesday.
"We have to find out what 'it' is."
Pierce told ESPN.com that he wasn't concerned about a first-round playoff series against the Raptors, despite the fact Toronto has won all three regular-season matchups with the Washington Wizards.
"We haven't done particularly well against Toronto, but I don't feel they have the 'It' that makes you worried,'' Pierce said. "There isn't a team I look at in the Eastern Conference that makes me say, 'They are intimidating, we don't have a chance.'"
Pierce was already in Raptors' fans bad books. With Brooklyn last season, Pierce blocked Kyle Lowry's final shot of Game 7 of their opening round of the playoffs to clinch the series for Brooklyn. His comment to ESPN was more fuel for the fire.
When asked if Pierce's comment was about intimidation, Casey said" "I have no clue, you would have to ask him, I don't know what he's talking about, what 'it' is, I know our guys come out and compete every night, go hard.
"So whatever he means 'it' is, you have to ask him when you see him," he added laughing. "Or text him. Or Instagram him."