Because of that potential and other deals that have been made, there has been talk about whether the Red Sox will attempt to give Mayer a long-term extension before he establishes himself at the big league level.

However, according to Chris Cotillo, no conversation has taken place between Mayer and the Red Sox.
“More on an earlier point from the spring: Red Sox have never approached Marcelo Mayer on a long-term deal and that remains the case, FWIW,” he wrote.
While some teams aggressively pursue early extensions with young players, especially the Red Sox, it’s not the worst idea to wait. In Mayer’s case, Boston should be focused on allowing him to continue developing without adding the pressure of contract negotiations.
We all saw how bad things went for Kristian Campbell. If Mayer eventually plays well enough to get a deal, things will fall in place. There’s plenty of time before the Red Sox have to deal with that, though.