Mayock said Friday that he holds himself responsible for the ill-fated trade for the receiver, who was released on Sept. 7 before playing a single regular-season snap for Oakland.
"I put that on me," Mayock told Vic Tafur of The Athletic. "My anticipation was that he was coming off a situation in Pittsburgh where he wants to prove everybody wrong, and he wants to ride into the Hall of Fame. That he was going to come in with Jon Gruden and Derek Carr and our offense and lead the way. ... I really thought we were going to get the best out of Antonio Brown, and we didn't.
"We weren't able to get anything out of him. So, at the end of the day, in hindsight, we lost a third-round pick and a fifth-round pick, and I can't tell you how much pain that causes me."
Brown was cut two days after threatening to punch Mayock in the face and being restrained by teammates at practice due to his unhappiness with recent fines from the team.
The altercation was the culmination of an offseason of troubles for Brown, which notably included his threat to retire over helmet issues.
While the emergence of tight end Darren Waller and rookie receiver Hunter Renfrow helped fill the void, the Raiders' offense still struggled to adapt throughout the season after preparing to center their passing attack around the All-Pro's talents.
Oakland finished ninth in passing yards per game but only managed to average 19.6 points, which was tied for 23rd.
Brown ultimately played in only one game this season, for the New England Patriots, before again being released after he was accused of raping his former personal trainer in a civil lawsuit.
The receiver's NFL future remains in question pending the results of the league's personal conduct investigation.
Brown's chances of continuing his career were reportedly dealt a further blow Thursday when his longtime agent, Drew Rosenhaus, terminated their relationship until the wideout agrees to seek counsel.