The Eagles' decision to cut ties with one of the most electrifying players in club history last week came after the team uncovered information about Jackson's off-field connections and activities, a source told ESPN NFL Insider Adam Schefter.
Shortly before Jackson's release from the Eagles, NJ.com published a story discussing Jackson's alleged gang connections. Jackson refuted that report.
Smith said the NFLPA will examine whether the Eagles leaked comments or misinformation to the media about Jackson, who signed a three-year contract with the Redskins on Wednesday. That deal is worth $24 million, including $16 million guaranteed, according to league sources.
"That's something that we're going to look at," Smith said on ESPN's "Mike & Mike" show. "We've always been aggressive about protecting the integrity of our players, especially where we believe or think that a team may have done something that is impermissible, and that's something that we're gonna look at."
The Eagles issued a statement saying they decided to release Jackson "after careful consideration." The team has withheld further comment.
A league source told ESPN's Sal Paolantonio that the Eagles decided to release Jackson for a number of reasons due mostly to "work ethic and attitude."
"You're talking to a guy who spent 10 years as a federal prosecutor in Washington, D.C., and I grew up in the city ... to have someone come out and say 'gang affiliation,' I'm not sure I know what that means," Smith said. "I certainly know what it means to prosecute members of a gang. I certainly know what it means to be a member of organized crime. I don't know what it means when a team or an official says that there's 'gang affiliations.'
"To me, the real issue is this is the business of football. If you want to make a decision to cut a player, tell a player he's cut. Make a decision. But if you want to smear a player with innuendo or something that is less than proof ... you know that I was very aggressive in calling a few GMs cowards for what they said about a young man coming out of college [former Missouri defensive end Michael Sam]. It seems to me that the same thing applies ... if you want to smear someone and you don't have any evidence."
Jackson was set to be interviewed by ESPN's Stephen A. Smith later Friday. That interview is scheduled to be aired on "SportsCenter" at 6 p.m. ET.
NFL To Probe DeSean Jackson's Release
DeMaurice Smith, the executive director of the NFL Players' association, said the union will look into DeSean Jackson's release by the Eagles.