DENVER—Rookie Patrick Surtain II picked off Justin Herbert twice, returning the second one 70 yards for a touchdown and sparking the Denver Broncos’ 28-7 win over the Los Angeles Chargers on Sunday. The Broncos’ big win sets up a showdown for the AFC West lead next weekend in Kansas City, where the game between Denver (6-5) and the Chiefs (7-4) already was flexed to Sunday night. Surtain’s first interception came in the end zone on a pass intended for tight end Jared Cook early in the fourth quarter. The Broncos converted that takeaway into a touchdown when Teddy Bridgewater hit tight end Eric Saubert from 9 yards to make it 21-7. His second one came off the hands of Austin Ekeler, who watched helplessly as Surtain cradled his second interception and sprinted down the Broncos’ jubilant sideline to push Denver’s lead to 28-7. Denver’s defense came up big on a …