Christian McCaffrey of the San Francisco 49ers has been ruled inactive for Week 1 due to a calf/Achilles injury that has plagued him since early August. The team will rely on Jordan Mason to fill the void in the backfield. Earlier in the week, McCaffrey had expressed confidence about playing and handling his usual workload, but ultimately, he will not be on the field against the Jets.

• McCaffrey's absence will impact the 49ers' offensive strategy in Week 1.
• Jordan Mason is expected to take over the primary running back duties.