Clay Matthews, Julius Peppers, and James Harrison - all named in Al Jazeera America's PED report - have agreed to be interviewed by the NFL, ESPN's Chris Mortensen reports.

Harrison will interview at the Pittsburgh Steelers' facility Aug. 29, according to an NFLPA letter to the NFL acquired by ESPN. The linebacker has asked that questions pertain to the excerpt in which he is cited in the report.

Related: NFLPA: League trying to bully, shame Harrison with PED investigation

Free-agent linebacker Mike Neal, also named in the report, will not agree to an interview, a source told Pro Football Talk.

An interview date hasn't been determined for Matthews and Peppers, both Green Bay Packers linebackers.

The league informed the NFLPA that the four players in question had to be interviewed by Aug. 25 or face suspension.

In the report in question - a documentary entitled "The Dark Side" - former Guyer Clinic pharmacist Charlie Sly alleged the players were linked to PEDs. Now-retired quarterback Peyton Manning was also mentioned in regards to human growth hormone, but he was cleared of any wrongdoing by the NFL in July.