What you need to know

• The 49ers fall to 3-4 with a tough 28-18 loss to the Chiefs, who improve to 6-0. Kansas City is now the NFL’s only undefeated team after the Minnesota Vikings lost to the Detroit Lions on Sunday.
• Just before the game, the 49ers announced that wide receiver Deebo Samuel was dealing with an illness but was expected to play. He entered the field for the first drive, but was unable to play afterward. He went to the locker room late in the second quarter and was ruled out shortly after halftime.
• Brandon Aiyuk suffered a right knee injury with 37 seconds left in the second quarter and was ruled out early in the third quarter. The All-Pro wide receiver, who finished with two receptions for 23 yards, was able to limp off the field, but he was wheeled to the locker room, and coach Kyle Shanahan later said he feared Aiyuk had suffered a torn ACL.
• Rookie wide receiver Ricky Pearsall made his NFL debut nearly seven weeks after suffering a gunshot wound during an attempted robbery on Aug. 31 in downtown San Francisco. The 2024 first-round draft pick caught three passes for 21 yards on five targets.
• Quarterback Brock Purdy had one of the worst games of his NFL career, completing 17 of 31 passes for 212 yards with no touchdowns, three interceptions and a career-worst 36.7 rating. He scored the 49ers’ only two touchdowns of the game on two 1-yard TD runs.
• The 49ers now have to lick their wounds — both literally and figuratively — as they prepare to host the Dallas Cowboys next weekend on NBC’s “Sunday Night Football.”