FIRST QUARTER SPELLS DISASTER; WEBSTER SUFFERS A CONCUSSION

kansas city, mo.» The Broncos gained only 12 yards on six plays on their opening possession Sunday. The Chiefs responded with seven plays and 77 yards, ending with a 10-yard touchdown run by quarterback Alex Smith. It was the seventh touchdown allowed this season by Denver’s defense on an opponent’s first possession, tied for the second-most in the NFL.

The Chiefs later in the first quarter scored on a 70-yard run by Tyreek Hill and an 80-yard reception by tight end Travis Kelce, the longest run and pass plays allowed by Denver this season. All told, in the first quarter Kansas City amassed 243 yards and three touchdowns, compared with Denver’s 57 yards and one touchdown (a 1-yard run by Justin Forsett after an interception by Denver safety Justin Simmons was returned to Kansas City’s 6-yard line). The Chiefs bolted to a 21-7 lead.

Denver has a minus-61 firstquarter scoring differential, second-worst in the NFL.

Injury report. Broncos cornerback Kayvon Webster suffered a concussion after taking a hard hit to his helmet on kickoff coverage in the first half. Webster was down on the field for a few minutes, with players on both sides retreating to a knee. Webster was able to get to his feet before being carted off.

Defensive end Derek Wolfe reinjured his neck during the first half, an injury that caused him to miss practice all week, and did not return to the game.

Running kicker. Brandon McManus’ 52-yard field goal in the second quarter was his third 50-yarder this season and the eighth of his NFL career. He ranks third on Denver’s all-time list in that category, behind Jason Elam (37) and Matt Prater (21).

McManus ran for 6 yards on a failed fake field-goal attempt late in the second quarter, which was only the second recorded run by a place-kicker in Broncos history. Elam had the first, a 2-yard run against Seattle in 2006 that earned a first down.

Inactive players. The Broncos were missing four key contributors because of injuries. Safety T.J. Ward and tight ends A.J. Derby and Virgil Green, all in the concussion protocol, and inside linebacker Brandon Marshall (hamstring) were among the Broncos’ seven inactive players Sunday. Inside linebacker Quentin Gause, offensive lineman Connor McGovern and outside linebacker Vontarrius Dora filled out the list as healthy scratches.

Footnotes. Von Miller, Aqib Talib and Chris Harris were the game-day captains for the Broncos. … Sunday was Demaryius Thomas’ 29th birthday. Monday is Trevor Siemian’s 25th birthday.