Sorting through defensive linemen a difficult task for 49ers

SANTA CLARA, Calif. -- The San Francisco 49ers will report for training camp July 27, with the first practice slated for the following day.

As we head toward the start of camp, we're previewing each position and the competitions that could ensue. Today we look at the defensive line, a place where the Niners have invested heavily in the draft and free agency in recent years and where there's going to be some intense competition for jobs in the coming weeks.

On the roster: DeForest Buckner, Arik Armstead, Earl Mitchell, Solomon Thomas, Tank Carradine, Chris Jones, D.J. Jones, Quinton Dial, Elvis Dumervil, Ronald Blair, Noble Nwachukwu, Aaron Lynch, Pita Taumoepenu

Locked in: Buckner, Armstead, Mitchell, Thomas, Dumervil

Battles to watch: Of all the potential camp battles that could take place this summer, this one has the makings of being the most heated. The 49ers are switching to a 4-3 scheme under coordinator Robert Saleh, which means there is room for more defensive linemen. Although we don't know exactly how many the Niners will keep, it's a good bet there will be eight or nine when camp is finished. And that doesn't even include the Sam linebacker position, which technically falls under the control of the defensive line and coach Jeff Zgonina.

At the outset of camp, it's probably safe to assume that Buckner, Armstead, Mitchell, Thomas and Dumervil will be around. The first four are likely to start at the 3-technique defensive tackle, Leo defensive end, nose tackle and big defensive end positions, respectively. Dumervil was signed to add pass-rush pop, presumably in a rotational role behind Armstead.

Where the real battles begin are for the rest of the depth spots on the line. Zgonina made it clear in the spring that competition will be heated in camp. If those first five solidify their spots, that means three or four jobs will be up for grabs in camp. Those jobs will likely come down to a battle among Carradine, Chris Jones, D.J. Jones, Dial, Blair, Lynch and Taumoepenu.

Starting with the big defensive end spot, Carradine handled most of the starting reps while Thomas was waiting for Stanford to finish school. Carradine had a solid camp and appeared to finally be comfortable in a position. He would seem to have an inside track on a job but will get stiff competition from Blair, who has enough versatility to move inside on passing downs.

At nose tackle, Mitchell came aboard as a free agent in the offseason, and the Niners will need another big body to back him up. That competition figures to come down to Dial, Chris Jones and D.J. Jones. Dial has the experience but D.J. Jones is a promising rookie with some upside. Chris Jones has earned rave reviews from the coaching staff for his work ethic and strength. The 3-technique tackle spot behind Buckner could include Blair, Chris Jones and even Dial.

The Leo defensive end spot is reserved for the best pass-rushers, and with Armstead and Dumervil likely to nail down two spots, a third spot would have to go to someone with the versatility to play multiple places. Lynch offers the most upside but has battled weight issues and has never fully tapped into his potential. Taumoepenu is another rookie with some upside, but he could be stashed on the practice squad for a year or two before making an impact on the roster.

While the Niners will have padded practices in training camp, it can still be hard to fully determine what a defensive lineman brings without playing in games. Which means those preseason contests will go a long way to determining which defensive linemen earn their way on the roster.