The 26-year-old was a first-team All-Pro in 2019 after catching 85 passes for 1,053 yards and five touchdowns. Football Outsiders ranked him fourth in DYAR (defense-adjusted yards above replacement) among tight ends.
Minor injuries to his ankle and knee kept Kittle out for two games, while he said in January he had been playing through a torn labrum since the 2018 season.
It's impossible to overstate the Iowa product's importance to the 49ers passing game. He was the team's leading receiver last year, with Deebo Samuel finishing second (802 yards).
Samuel underwent surgery for a Jones fracture in June, and he was placed on injured reserve last Saturday.
And rather than signing a proven veteran to replace Emmanuel Sanders, who left via free agency, San Francisco selected Arizona State wideout Brandon Aiyuk with the 25th overall pick in the 2020 draft. Aiyuk missed the season-opening loss to the Arizona Cardinals with a hamstring strain, but he could make his debut Sunday against the New York Jets.
The Niners signed Mohamed Sanu this week, and the veteran could play in New York.
Ross Dwelley, who had 17 total receptions between 2018 and 2019, will likely replace Kittle at tight end, so it will be up to the team's wide receivers to pick up the slack with the two-time Pro Bowler out of action.