Kittle sustained the injury during Sunday's Week 1 matchup against the Seattle Seahawks early in the second half while blocking safety Julian Love. However, Kittle still managed to put up a touchdown of his own before officially exiting the game.
Backup tight end Jake Tonges received the majority of the work in place of Kittle, including a go-ahead touchdown catch that eventually led to their 17-13 win.
It was Tonges' first-ever NFL touchdown since entering the league as an undrafted free agent in 2022.
Kittle, who has been relatively healthy the past four seasons, will now go down as yet another significant injury on the 49ers' league-leading IL.
Quarterback Brock Purdy, who also sustained an injury on Sunday, is questionable for Week 2's matchup against the New Orleans Saints. If Purdy isn't healthy, they'll have to rely on backup Mac Jones to get the job done.