"Yo @sammywatkins I'd love to squad up and have you on the squad! Come on over to Cincy with my dawgs," Mixon tweeted on Tuesday.
"You never know brother this business is crazy," Watkins tweeted on Thursday.
Mixon acknowledged Watkins' reply by saying he would be welcome in Cincinnati and wished him well.
The exchange comes on the heels of the Los Angeles Rams electing to apply the non-exclusive franchise tag on safety Lamarcus Joyner, as opposed to Watkins.
Watkins had 39 receptions for 593 yards and a team-leading eight touchdown catches this past season. The 24-year-old, however, had three or fewer catches in 12 of 15 games this past season.