As if it hadn’t been through enough, things went from bad to worse for the Chargers offensive line today when offensive tackle Joe Alt was carted off the field with an ankle injury, per Ian Rapoport of NFL Network. Rapoport followed up that report with news that X-rays on the ankle came back negative for broken bones but that a high ankle sprain was the preliminary diagnosis. Alt will undergo MRI testing tomorrow to determine the severity of the injury. 
The Chargers came into today down two starters on the offensive line already. Regular left tackle Rashawn Slater is already out for the season with a torn patellar tendon, and starting right guard Mekhi Becton was ruled out for Week 4’s game due to a concussion. They lost their third starter on the line when Alt was carted off, leaving only center Bradley Bozeman and left guard Zion Johnson as the last of the original first-team offensive line remaining.
While we know Slater isn’t coming back to the field until next year, Becton should be back as soon as he clears concussion protocol. Alt’s timetable for return will depend on the results of the upcoming MRI. A high ankle sprain usually means an absence of, at least, a couple weeks. If the injury is severe enough, it could take months for Alt to return to the line. An absence of that length would be brutal for a team that has had such a promising start to the season.
Alt was only playing left tackle for the Chargers because of Slater’s injury. With Alt vacating the right tackle spot he played in his rookie campaign, Los Angeles has been starting Trey Pipkins on the right side. When the Chargers lost their second left tackle in as many months, it was Austin Deculus who came in to fill out the first-team offensive line at left tackle.
Pipkins had had prior experience as a starting tackle for the Chargers, though his time in that role was partially the reason for the team drafting Alt. He shifted in to a starting guard spot once Alt came in, but his return to a starting tackle role was not a necessarily difficult move. Deculus, on the other hand, has only started one game in his four-year NFL career, and even including that start, he has never played more than 38 snaps in an NFL game.
Deculus’ lack of experience is only a potential concern if Alt’s MRI comes back with bad news. If it turns out that the Alt is in for an extended absence, the Chargers will have to navigate that time with two backup tackles. They should know more about what they’re dealing with tomorrow.