The Rennes centre-back has been on the radar of manager Steven Gerrard, who flew to France to watch the player in action last week.
Mexer will be available on a free transfer this summer with the 30-year-old’s contract winding down.
The Mozambique international wrote alongside a picture on Instagram: “Walking to the future.”
Candeias then replied with: “The future is here my ferer [friend].”
The two are former teammates from their time together at Nacional in the Portuguese top flight. Candeias spent four years there from 2010 to 2014, while Mexer joined in 2012 before leaving the same summer as the Rangers winger.