Foster, in need of reps, gets lots in Kansas City

KANSAS CITY, Mo. — Four days after 49ers defensive coordinator

Robert Saleh said Reuben Foster needed “reps, over and over and over again,” the rookie inside linebacker got them Friday night.

The 31st overall pick, Foster was one of four defensive starters who played the entire first half of the preseason opener.

Foster, joined by defensive tackle Tank Carradine, cornerback Keith Reaser and undrafted rookie safety Lorenzo Jerome, had a relatively quiet preseason debut. He began by breaking up a would-be touchdown pass intended for Chiefs tight end Demetrius Harris on the game’s opening drive and finished with two tackles. Foster has been thrust into the starting lineup because Malcolm Smith suffered a season-ending pectoral injury last week.

Meanwhile, defensive tackle Solomon Thomas, the No. 3 overall pick, made an immediate impact: On his first snap, midway through the first quarter, Thomas pressured quarterback Tyler

Bray, who floated an interception to cornerback Rashard Robinson.

In an interesting development with a less heralded rookie, Matt Breida, who was undrafted out of Georgia Southern, was the first running back off the bench instead of fourth-round pick Joe Williams. Breida has looked more impressive than Williams in training camp, but the roles were reversed in the first half: Williams had 34 yards on three carries, while Breida had 17 yards on eight attempts. Injury report: Defensive tackle DeForest Buckner exited on the first drive with an ankle injury, and the team quickly announced he wouldn’t return to the game.

However, Buckner, who was sidelined by an ankle injury in training camp, did not appear to be seriously hurt. He stood on the sideline after leaving, joked with his teammates on the bench and jogged slowly off the field at halftime. Cornerback Dontae Johnson (concussion), running back Tim Hightower (knee), safety Jaquiski Tartt (rib), rookie tight end George Kittle (hamstring), guard Joshua Garnett (knee), safety Jimmie Ward (hamstring) and linebackers Donavin Newsom (concussion) and Brock

Coyle (rib) did not play. Newsom, an undrafted rookie who left the practice field in an ambulance Tuesday, was released from Stanford Hospital on Thursday after spending two days under observation. Captains: Left tackle Joe Staley, inside linebacker Na Vorro Bowman and wide receiver Aaron

Burbridge (special teams) were named team captains for the game.

The designation is a good sign for Burbridge, the team’s top gunner who is battling for a spot. Burbridge, a 2016 sixthround pick, had seven catches for 88 yards as a rookie.

Burbridge (hamstring) was declared out of the game at halftime.