They added a second building block during the free-agent signing period by bringing in running back Jerick McKinnon, giving Garoppolo a two-way threat out of the backfield.
As it turned out, the two marquee acquisitions never got a chance to play a down together in a regular-season game for the 49ers and won't have a chance to do so until at least the 2019 season.
Garoppolo, who won all five starts to wrap up 2017 and was the biggest source for the lofty expectations in the Bay Area, is done for the year after suffering a torn ACL in last week's 38-27 loss at the Kansas City Chiefs.
It was the latest crushing blow for San Francisco, which lost McKinnon to a similar injury in the preseason.
"I'm not going to sugarcoat it, it was hard waking up today," 49ers head coach Kyle Shanahan said after Garoppolo blew out his left knee trying to make a cut on the sideline late in last Sunday's loss. "We were looking forward a lot to playing with Jimmy this year and going through the good and the bad that would happen, knowing that he would benefit from all of it. Now, we don't get to do that.
"This is part of the league. It's part of the NFL. It's part of life. You have to adjust to it and you've got to make the best out of it."
Perhaps the most sobering reminder for San Francisco fans is the fact that the team was 1-10 the last time Garoppolo was not in the starting lineup.
C.J. Beathard, a third-round pick in the 2017 NFL Draft who started five games last season, will step in for Garoppolo. Beathard completed 55 percent of his passes last season while throwing for four touchdowns against six interceptions. In last week's game, Beathard attempted only one pass for an apparent touchdown, only to see it negated by penalty.
"He played in six games last year and beat the Giants," pointed out Chargers head coach Anthony Lynn. "He can move around a little bit; they do more things with him. I believe he can function well in that offense."
Much like the 49ers, Los Angeles built heightened expectations with a strong finish to the 2017 season, winning six of its last seven games. The Chargers, though, are also off to a 1-2 start with the only win coming at the Buffalo Bills in Week 2.
Slow starts have been commonplace for Los Angeles, which owns a 1-6 record in September over the last two seasons.
The Chargers have been unable to stop the opposition, giving up 93 points and negating an offense that is averaging 27.3 points. They have been hurt by the absence of Pro Bowl defensive end Joey Bosa, who had 12.5 sacks last season but has been hobbled since early August due to a foot injury.
Quarterback Philip Rivers has thrown for eight touchdowns and only one interception while averaging just over 300 passing yards per game. Wideout Keenan Allen has 26 catches for 219 yards and a score while running back Melvin Gordon has accounted for four touchdowns, rushing for 172 yards and hauling in 24 receptions.
"It's exciting as a quarterback to know we can do so many things," said Rivers. "We are not limited in what we can do week-to-week.
"We're running the heck out of the ball right now, averaging 5.5 yards per carry and that's huge. The offense feels really balanced and that's why we are getting a lot of first downs. The more first downs you get the more chances you get to throw it and run it."
Despite the loss of McKinnon, San Francisco also features a potent ground game, ranking second in the NFL in rushing. Matt Breida is tied for the league lead with 274 yards rushing, but he was limited in practice Wednesday due to a hyperextended knee.
The 49ers will also be without one of their top defensive players. Cornerback Richard Sherman suffered a calf injury in the loss at Kansas City and is expected to be sidelined for at least the next two games.