As reported earlier this week, Chargers quarterback Justin Herbert underwent surgery to address a broken bone in his left (non-throwing) hand. Per Nick Shook of NFL.com, while the 27-year-old passer is still considered day-to-day at the moment, the team — specifically head coach Jim Harbaugh — is “optimistic” that Herbert will be the one under center to start the game on Monday night. 
According to Omar Ruiz of NFL Network, Herbert described the surgery, telling reporters that a plate and a few screws were put into his hand during the procedure. The current plan is just to prepare as is he’s starting against the Eagles this week, though an eye will be kept on his hand to determine if the swelling from the surgery has subsided enough for him to play. In Week 13, he wore a glove on his left hand made to stabilize the injury, and a similar technique could be utilized again in order to stabilize his healing hand.
While Harbaugh is optimistic, and Herbert is preparing like he’s starting, Harbaugh is not depending solely on Herbert. According to ESPN’s Dan Graziano, backup quarterback Trey Lance is expected to get some run with the first-team offense this week, in case the team feels Herbert’s hand won’t allow him to “function in enough basic ways or protect himself if he falls.” Lance, a former No. 3 overall pick, started four games in his first two years in San Francisco but has only logged one start in the past three seasons combined. If Herbert’s hand hinders him in the ways quoted above, though, Lance would be tapped as the starter.
Lance took all of the first-team reps in today’s practice, with Herbert not practicing in the traditional sense and, instead, being present on the field through the first sessions of practice. Even if Herbert’s hand is doing well enough for him to start, Lance’s work with the first team could still be handy for certain situations.
Herbert’s hand may prevent him from being literally under center since it could be difficult for him to receive snaps between the center’s legs with the injury. Herbert can try to stay in shotgun formations as much as possible, but in short yardage or goal line situations, the team may rely on Lance, whose hand would be less at risk of injury in a scrum.
The news on the matter is still not definitive, but at least we now know what to keep an eye on in the days to come. As long as Herbert and Co. can get the swelling down over the next five days, he should return as starter. In the meantime, Lance will continue preparing for roles both big and small.
I really think for safety sake he should miss Monday night.