Expectations were high in San Francisco this season that the team could end a four-year playoff drought after Garoppolo had a full offseason to immerse himself in coach Kyle Shanahan's offense.
It's official, Jimmy Garoppolo is done for the year.
Garoppolo joins running back Jerick McKinnon, the 49ers' marquee free-agent acquisition who also suffered a torn ACL before the start of the season. That's when the San Francisco quarterback headed for the sideline. The team had acquired him in a trade with the New England Patriots during the middle of last season for a second round pick.More news: Trump backs Supreme Court nominee Kavanaugh amid fresh allegation
The Niners struggled with Beathard and Brian Hoyer last season before the midseason addition of Garoppolo changed their fortunes.
With Garoppolo on the shelf, San Francisco will hand quarterback duties to C.J. Beathard.
Through three games this season, he had completed just under 60 percent of his passes for 718 yards with five touchdowns and three interceptions as the 49ers got out to a 1-2 start.
Kaepernick went 28-30 in five years as the 49ers' starter, throwing for 12,271 yards and 72 touchdowns.