SANTA CLARA, Calif. (AP) Quinton Dial is running with the first-team defense for the San Francisco 49ers, who are looking to once again turn a young, raw prospect into a producer along their defensive line after the departure of long-time starters Ray McDonald and five-time Pro Bowler Justin Smith.

As the team prepares for its first practice in pads Tuesday, Dial isn't the only unheralded youngster that could play a prominent role on a line groomed the past eight seasons by Jim Tomsula, now entering his debut season as San Francisco's head coach. The revamped front will have several faces who have followed a similar path.

Since joining the 49ers as their defensive line coach in 2007 - a position he held until being promoted in January to replace the departed Jim Harbaugh - Tomsula has mentored several projects and undrafted prospects into productive players along a unit that has anchored one of the NFL's top defenses of the past five seasons.

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Dial is one of them. Drafted in the fifth round out of Alabama in 2013, he appeared in only three games and recorded two tackles as a rookie. But last year, when injuries rocked San Francisco at nose tackle, the 6-foot-5, 318-pound Dial got an opportunity to step in and started six of the 49ers' final seven games.

This summer, with Ian Williams and Glenn Dorsey back from injuries that ended their seasons last year, Dial is sliding over to right tackle and relishing a chance to continue his progress at a new position now that the hitting finally will begin.

''I can't wait, man,'' Dial said Monday. ''It's a great opportunity and something I've been looking forward to for a long time. Doing all this offseason training, pushing weights, somebody's got to pay for the work I've been putting in. Can't wait.''

Without McDonald and Smith - regular starters at tackle since 2011 in San Francisco's 3-4 defensive scheme - several youngsters whom Tomsula has developed are getting opportunities this summer for bigger roles.

Smith retired in May after 14 decorated seasons. McDonald was released abruptly last December due to off-field issues after starting San Francisco's first 14 games at left tackle.

That has left significant voids along the defensive front on each side of Williams, who is settling back in as the starting nose tackle for the third consecutive summer. Dial is getting a legitimate shot to replace Smith.

''I watch a lot of tape of Justin,'' Dial said. ''The last two years I was with him I asked a lot of questions and worked with him on some stuff, and what I've learned from him I try to put in my game. Everybody plays different. And playing D-line, it's pretty much playing the same positions. You all see the same blocks. It's helped me a lot to get ready for this opportunity.''

Dial got his first career start last November when a fractured fibula ended Williams' season after eight starts.

Williams, who joined the 49ers as an undrafted rookie in 2011, was one of several undrafted players who became defensive line starters under Tomsula's tutelage, including Tony Jerod-Eddie and DeMarcus Dobbs.

Jerod-Eddie, who started the final two games at left tackle in place of McDonald last season, also is in the mix for extensive playing time, along with Lawrence Okoye, another undrafted project who may be ready this summer.

Okoye competed for England as a discus thrower in the 2012 Olympics. He had never played a snap of organized football before the 49ers signed him in 2013. Too raw to play immediately, Okoye enters his third season still waiting for his first NFL action. He spent his rookie season on injured reserve and was on San Francisco's practice squad last season.

An imposing figure along the front at 6-6 and 304 pounds, the muscle-bound Okoye says he's finally ready to contribute like the unheralded prospects before him.

''I remember when I first got here, the first thing Jimmy (Tomsula) told me was, if you want to play in the NFL, and you're a defensive lineman, the best place to be is here,'' Okoye said. ''He has honed me to a point where I can play in the NFL now. The track record speaks for itself, the number of undrafted guys that have gone through this system to start their careers and done well.''

It's not just longshots looking to move up. Rookie first-round draft pick Arik Armstead, 2013 second-round pick Tank Carradine and former first-rounder Glenn Dorsey also are in the thick of the competition.

But Dial has made an impression during the non-padded opening days of camp, attempting to make the open spot his job to lose.

''Q is a tough, hard-working, feisty guy,'' Okoye said. ''I mean, anyone in this locker room will tell you that. He's one of the toughest guys you'll run across, and he's earned his position.''