What happened: Hartwig joins Detroit after becoming a free agent June 8. He brings experience at center and guard.
Why it matters: The move adds interior-line depth before final preseason roster decisions. His positional flexibility could help in the reserve competition.
By the numbers: Hartwig started 45 college games at center after beginning his career at guard.
What to watch: Watch Hartwig's practice reps and whether he earns a spot on Detroit's initial 53-man roster.