Mortensen later added on Twitter that "nobody," including Lynch, expects the running back to return to the team in 2015 but that the team isn't considering trading him before Tuesday's trade deadline.
It's unclear exactly what behaviors have led to Seattle's reported decision to not bring Lynch back.
According to NFL Network's Mike Silver, Lynch feels bitter toward head coach Pete Carroll due to his contract issues and heavy workload the past few seasons.
Lynch signed a four-year contract with the team in 2012 and is due to make $5 million in salary next season and potentially as much as $2.5 million more in roster bonuses. He held out at the beginning of training camp this year in an attempt to garner more money but eventually capitulated and returned to the team, with the Seahawks adding financial considerations to his contract.
Carroll said before the season that Lynch looked "the best we've seen him" at that time of the year despite his holdout.
The 28-year-old is known for rarely speaking expansively to the media, and agreed to participate in media sessions last season only when faced with the possibility of a large fine from the NFL. He reportedly refused to get on the team's bus before its game against the St. Louis Rams last week after learning that Seattle had traded receiver Percy Harvin to the New York Jets, though Lynch's agent refuted the report.
Lynch has been with the Seahawks since they acquired him in a trade from the Buffalo Bills in 2010. He's led the NFL in carries over the last three seasons while making the Pro Bowl each year, rushing for a total of 5,044 yards and 44 touchdowns in his time with Seattle.
Lynch has 97 carries for 420 yards and three touchdowns this season. He's on pace for 1,120 rushing yards, which would be his lowest total since 2010.
The Seahawks are 3-3 this season and in third place in the NFC West. They play the Carolina Panthers on Sunday.
- Ben Estes