SANTA CLARA — Bryce Treggs’ daunting quest to make the 49ers roster began in March, when head coach Chip Kelly and team officials held a pre-draft workout for Treggs’ more heralded Cal teammate, Jared Goff.

While Goff eventually went No. 1 overall to the Los Angeles Rams, Treggs went undrafted — but not undeterred. After initially talking to Kelly at Cal’s pro-day session, Treggs became more enamored with the 49ers new coach through Goff’s private workout.

“Chip Kelly was walking me through every route, showing me some of the things they do,” Treggs recalled Sunday. “That’s when I really, really decided that this is probably the right spot for me, because of how interested Chip Kelly was.”

Treggs, who ran a 4.39-second 40-yard dash at Cal’s pro day, is an intriguing option for a youth-laden, mostly unproven receiving corps.

On Sunday, Treggs caught three consecutive passes from Thad Lewis on the third-string unit, flashing the speed and playmaking ability that must remain present to steal a roster spot, or at least a practice-squad role.

“His offense definitely puts speedy guys like me in position to make plays,” Treggs said. “I’m trying to embrace that role and bring a different aspect to the team, something that they don’t have, and that’s a real, solid deep threat out of the slot.”

Bruce Ellington is the incumbent slot receiver, and when healthy, he’s a versatile weapon. Ellington has 19 career receptions, with a career-long of 44 yards, plus two touchdowns in two seasons.

Both Ellington and Treggs said they’ve studied how Jordan Matthews flourished as a slot receiver in Kelly’s Philadelphia Eagles offense the past two years.

“I can be the same type of player as far as in the slot making big plays,” Ellington said of Matthews. “I feel I’m the type of playmaker where you can line me up anywhere, and I can do what I’ve got to do.”

Kelly needs as many playmakers as possible in an up-tempo attack that will be run-oriented. If Treggs has a big preseason, that wouldn’t be a shock.

“He was a guy that we felt would fit in the mold,” Kelly said of Treggs as a slot receiver. “He’s a lot similarly built, similarly sized to Bruce (Ellington). They both kind of have the same qualities in there.”

Treggs is 6-foot with a strong upper body. He combines short-area quickness to separate off the line of scrimmage and deep-threat speed to stretch a defense, Kelly added.

Eric Rogers’ exit with a season-ending knee injury Friday means there is one less competitor in the wide-open receiver race.

Among the challengers is DeAndrew White, who, like Ellington and Treggs, can line up in the slot and serve as a punt returner. Last year, White was the first undrafted wide receiver to make the 49ers season-opening roster since 2011.

Defensive linemen Arik Armstead and DeForest Buckner, the 49ers’ top draft picks the past two years, each left practice early Sunday with apparently minor arm injuries. A team spokesman did not believe either injury was serious. Armstead looked like he suffered a nerve stinger in his left shoulder while pass rushing against guard Andrew Tiller. About 15 snaps later, Buckner jogged off the field favoring his right arm after getting tangled with tight end Je’Ron Hamm and outside linebacker Tank Carradine. Although Buckner had worked his way up from the third-string to the starting unit this camp, Sunday’s first-string linemen were Armstead, Mike Purcell and Quinton Dial. Buckner, this year’s top draft pick and No. 7 overall, hasn’t necessarily been “promoted,” according to Kelly, who said coaches are experimenting with different lineups.

Colin Kaepernick struggled with his accuracy and precision in team drills, most of which involved short, horizontal throws. He completed just 4 of 10 passes in 11-on-11 action, and nearly had two of his final three throws intercepted by Keith Reaser. Kaepernick also fumbled on an apparent hand-off attempt to Shaun Draughn. Blaine Gabbert was 10 of 13, and he completed his final five throws, capped with a touchdown pass to Jerome Simpson. Kelly has not announced who will start the exhibition opener this Sunday at home against the Houston Texans.