Plenty of backup spots still unsettled for 49ers

SANTA CLARA - Brian Hoyer is the starter at quarterback, Carlos Hyde at running back. The starting five offensive linemen seem set and Reuben Foster has a comfortable lead at linebacker that he is unlikely to relinquish.

For a team in rebuilding mode, the 49ers appear to have few prominent roster battles as they head into the third and - say it in unison, “the most important” - preseason game of the summer. In fact, there may be only one, possibly two, starting spots up for grabs, although plenty of backup jobs remain fuzzy.

Starting strong-side linebacker: Here’s the competition in a nutshell: Ahmad Brooks is the better candidate now, but the 49ers might feel Eli Harold has more upside. He also is signed for one more year than Brooks. Something to keep in mind: Brooks has been remarkably durable since he became a starter in 2011, missing only three games (thumb injury and a concussion) over that span. Harold already has been hurt twice this year. (Of course, Brooks also was twice deactivated for behavior issues over that span.) Ironically, the third player in this mix, Dekoda Watson, may be the biggest lock because of his special-teams prowess.

Backup quarterback: Have two strong preseason performances won C.J. Beathard the No. 2 job over Matt Barkley? If Beathard is the first quarterback off the bench Sunday in Minnesota and he plays well, we can assume that he’s won the competition, at least for Week 1. At that point, it becomes a question of whether the 49ers keep two or three passers on the roster. The guess here is that Hoyer’s injury history prompts them to keep three.

Backup running back: Do the 49ers go with youth behind Hyde - rookies Joe Williams and Matt Breida - or do they want someone with experience, Tim Hightower, in that mix? Most observers have counted Kapri Bibbs and Raheem Mostert out of the running. But they’re good fits as well, and the group appears very much bunched together heading into Minnesota.

Three tight ends: George Kittle remains the only lock to make the team. After him, Logan Paulsen and Vance McDonald have been getting the most snaps with the first-team group. There’s still a question of whether the 49ers will trade McDonald, but that prospect seemed more likely in late April than it does in late August.

Offensive line backups: Who is the team’s swing tackle: John Theus or newcomer Garry Gilliam? Theus is eligible for the practice squad. If San Francisco cuts Gilliam, he might get gobbled up by his former team, the Seahawks, who lost left tackle George Fant for the season in their most recent game.

Tim Barnes appears to be in the lead for the role of backup center and guard. Undrafted Erik Magnuson also has been getting a long look at those positions.

Defensive-line depth: Tank Carradine so far has been able to hold off Solomon Thomas for the starting spot. The rookie’s presence might make Carradine a trade candidate, and both the Lions and Jaguars could use edge rushers. Meanwhile, do the 49ers keep two backup nose tackles in Quinton Dial and rookie D.J. Jones? How can they possibly keep four Leo pass rushers in Arik Armstead, Elvis Dumervil, Aaron Lynch and Pita Taumoepenu? Barring trades, the toughest trims will be along the defensive line.

Backup safety: Lorenzo Jerome will lose his starting spot at free safety when Jimmie Ward returns to practice. But he appears to have leapfrogged Vinnie Sunseri and Don Jones on the depth chart. That would leave Ward and Jerome as the top two free safeties and Eric Reid and Jaquiski Tartt as the top two strong safeties. If there’s room for one more, do the 49ers keep veteran Sunseri or rookie Adrian Colbert?

Cornerback: The top five are Rashard Robinson, Dontae Johnson, Keith Reaser, Ahkello Witherspoon and nickel back K’Waun Williams. Will Redmond was hurt for the last game, which doesn’t help his chances. Reaser and Jerome also can play nickel.