The Cleveland Browns wide receiver led the NFL in receiving yards last season, but is facing a year-long suspension for violating the league's substance-abuse policy and was arrested last week for a DWI offence.
The Arizona Cardinals safety, who was nominated for the Heisman Trophy in college before being suspended from the LSU football programme for substance abuse, told NFL Network: "Me, having been through it and having a little bit of experience with that, I don't think anybody in the world could possibly tell him anything.
"No one could tell me anything when I was going through it. I had to figure it out for myself. Hopefully he will get the point.
"Hopefully he will get the message, but most of the time it takes for people to hit rock bottom for them to start believing in their self and start seeking help. A lot of people can reach out to you, but that doesn't mean you always take that help and take that advice. He just has to want it for himself."
Mathieu made 68 tackles, a sack, a forced fumble and two interceptions during his rookie season in the league, before missing the end of the campaign with a knee ligament injury.