Guyton (ankle) did not participate in Monday's practice, Jon Machota of The Athletic reports.
Guyton was diagnosed with a high-ankle sprain following the Cowboys' Week 12 overtime win over the Eagles. The injury prevented him from playing against the Chiefs on Thanksgiving Day, and the second-year offensive lineman faces an uphill battle to be cleared to play Thursday against the Lions. Nate Thomas would be slated to start at left tackle for a second consecutive game if Guyton is ruled out.