Celek (back) announced his decision to retire from the NFL on Friday, Nick Wagoner of ESPN.com reports.
Celek appeared in five games with San Francisco in 2019, during which he contributed as a blocker across 63 snaps on offense. He spent the entire duration of his eight-year career with the 49ers, most notably having surpassed 300 receiving yards in two straight seasons with the team from 2016-17.