Olsen, who was released in February after nine seasons with the Carolina Panthers, was going to join Fox Sports this season if it wasn't for the deal with the Seahawks, Marchand adds.
Fox is reportedly willing to wait for Olsen even if 2020 isn't his final season, and he's expected to partner with Kevin Burkhardt in the broadcast booth.
The 35-year-old already appeared in multiple Fox Sports' XFL game broadcasts earlier this year.
Olsen's deal is reportedly similar to the one Drew Brees inked with NBC Sports. The New Orleans Saints quarterback will reportedly join the NFL telecasts once he ends his Hall of Fame-worthy career, and he could be in line to become Sunday Night Football color analyst Cris Collinsworth's successor.
The tight end was selected to three consecutive Pro Bowls from 2014 to 2016 after amassing at least 57 catches and 1,000 yards in each of those seasons. He posted 52 receptions for 597 yards and two touchdowns last year for Carolina.
He signed a one-year, $7-million deal with the Seahawks this offseason.