The San Francisco 49ers' worst fears were confirmed Monday, when franchise QB Jimmy Garoppolo's MRI on his left knee revealed a season-ending ACL tear, the team confirmed Monday.

Garoppolo was injured in the fourth quarter of the Niners' road loss to the Kansas City Chiefs on Sunday when his knee buckled near the end of a fourth-quarter scramble. Garoppolo, 26, signed an extension this offseason, his first in San Francisco following the blockbuster trade from New England last fall, containing over $74 million guaranteed. His first season as their full-time starter ends after only two-plus games, with a passer rating of 90.0, 5:3 TD-INT ratio and the Niners with a 1-2 record.

In Garoppolo's absence, the Niners initially will turn to C.J. Beathard, whom they surprisingly traded up to select in the third round of the 2017 draft. Beathard, the grandson of Hall of Fame personnel maven Bobby Beathard, went 1-4 as the starter in 2017 after replacing an ineffective Brian Hoyer, completing 54.9 percent of his passes for 4 TDs, 6 INTs and a 64.9 passer rating.

The Niners have now lost both of their big-ticket backfield acquisitions over the past year to non-contact knee injuries. Jerick McKinnon was signed to a top-5 veteran RB deal in the spring to be Kyle Shanahan's feature back but suffered his own season-ending injury in practice last month.

Should the 49ers kick the tires on another QB trade, perhaps for Cleveland's now-backup Tyrod Taylor? Our guess at the moment is that they won't. Shanahan has a reputation for resourcefulness and scheming great offensive production; now it'll be put to the test with Beathard at the controls beginning Sunday in L.A. vs. the Niners' fellow 1-2 CA resident, the Los Angeles Chargers.

San Francisco reportedly will also face Philip Rivers and Co. without top CB Richard Sherman, who will miss a few weeks with a calf strain, according to NFL Media. After playing Sunday without fellow starter Ahkello Witherspoon and appearing entirely out of sorts during a noncompetitive first half, Robert Saleh's 'D' visits a dangerous Bolts' WR corps including Comeback Player of the Year Keenan Allen and ascending Mike Williams, the seventh overall pick last year, coming off his first two-TD game.

If there's good news in Niners nation at the moment, it's that Reuben Foster avoided a scary-looking injury Sunday, and it appears upstart RB Matt Breida did, too.

Shanahan's club will need all the healthy bodies it can find if the Niners are to prevent their once-promising season from quickly going off the rails.