The 49ers believe Thomas may have sustained an ACL injury during Sunday's win over the Jets, Matt Maiocco of NBC Sports Bay Area reports.
Maiocco stopped short of saying Thomas tore his ACL, but the team will likely run an MRI to see the extent of the damage. With Nick Bosa expected to be done for the year with a confirmed torn ACL, Thomas' potential season-ending injury is another hit to team's defensive line.