Yes, Kenneth Walker's injury could affect the Chiefs for Week 1. According to the wiki, Walker was added to the Chiefs' "growing injury list" on August 25, which is just 20 days before their season opener against the Broncos (from the Chiefs page). The wiki doesn't specify the nature or severity of the injury, making his Week 1 status uncertain.
If Walker is limited or out, the Chiefs would lean more heavily on Isiah Pacheco as the lead back, with Emmett Johnson (PPR rank #182) potentially stepping into a larger role (from the Chiefs roster page). That's a significant downgrade from the explosive threat Walker was brought in to be — the Chiefs ranked 30th in explosive rush rate in 2025 and signed Walker specifically to fix that.
On Establish the Run, an analyst noted that with Mahomes recovering from ACL surgery and admitting he won't run this year, "that opens up more dump-off opportunities for Kenneth Walker" — . If Walker can't go, those check-downs likely go to Pacheco instead. The timing is especially rough given this is also a team dealing with Mahomes' own ACL recovery and Rashee Rice's off-field availability issues (from the Mahomes and Rice pages).