Where are 49ers’ big concerns entering preseason finale in Vegas?

SANTA CLARA – The 49ers don’t have enough pass rushers. They haven’t named a left guard. Their secondary is still shuffling. More than 20 players are hurt.

These are not new, alarming concerns. One preseason game remains to answer, if possible, how to shape the 49ers’ roster and decide a handful of jobs.

Thursday night’s closing act against the Raiders off the Las Vegas Strip, at Allegiant Stadium, likely only matters for fringe players and whatever injury fallout impacts Sunday’s 53-man roster deadline.

“It’s extremely fluid all the way up to the cutdown and after,” coach Kyle Shanahan said.

While a three-day cushion exists between the preseason finale and the first 53-man roster, the 49ers are on a double-decker plane three days later to Australia, so there is an urgency for the 49ers’ personnel department to fill jobs, both in-house and outside options via trade or the waiver wire.

“That’s one of their bigger challenges, just having to get everyone, get our practice squad ready, all that stuff a lot sooner than other teams are going to have to,” Shanahan added.

Here are three areas commanding attention, just as they did a month ago at the outset of camp:

1. EDGE RUSH POTENCY?

Too much is still resting on the comebacks of their starting-caliber defensive ends: Nick Bosa, Mykel Williams and Keion White.

Bosa paused his practices Aug. 3, but he and Shanahan are anticipating a Week 1 comeback from last season’s right ACL repair. Williams’ ACL comeback could be pushed to October if he opens the season on the Physically Unable to Perform list, but don’t be shocked if he’s cleared next week, too. White resumed practicing a week ago after an adductor injury, and after recovering in the spring from ankle surgery due to a gunshot wound at a Super Bowl afterparty.

Veteran Sam Okuayinonu figures to start at one spot, but a trade acquisition or a castoff veteran could, too. Rookie Romello Height is projected as an immediate rotational piece, but he missed practice this week with an ankle injury. Undrafted rookie Mikail Kamara was lost to an ACL early in camp, and of the seven (seven!) defensive ends who’ve signed since then, perhaps the most likely to stick is Ogba Okoronkwo. Victor Dimukeje had the lone sack and hit on a Chargers quarterback late in last Thursday’s preseason win.

2. GOOD GUARD

No position proved more of a turnstile in camp than first-string left guard. Connor Colby, a part-time starter there as a rookie, got first crack. Then came veteran Rob Jones, who stepped aside last week with a calf injury. Rookie Carver Willis, a tackle in college, has been getting the bulk of the work there lately. Austen Pleasants, left tackle Trent Williams’ understudy, got a shot at left guard until a knee injury in Thursday’s preseason win over the Chargers.

Willis, then Colby, are the frontrunners, merely because they’re the healthy ones. Jones has enough experience to resurface and plug in by kickoff in Australia. And what of Brett Toth, who missed all camp with a concussion but has plug-and-play potential?

The 49ers don’t need to publicly endorse anyone. It’s not as if this is high-stakes subterfuge that will mess with the Rams and potentially unretiring star Aaron Donald.

3. SECONDARY SHAKEUP

While the pass rush could benefit from versatile and aggressive schemes under first-year defensive coordinator Raheem Morris, he has some decisions to make with his secondary.

He could roll with last year’s unproductive unit that’s looked hungry and better in camp: Deommodore Lenoir and Renardo Green at outside cornerback, Upton Stout at nickel back, then Ji’Ayir Brown and Marquis Sigle at safety.

Or, Jack Jones could step in at outside cornerback, while Green deals with a hamstring injury. Or Lenoir could slide back inside at nickel. Or Malik Mustapha might return from a month-long hamstring injury to start at safety, likely next to Brown.

It might be that none of those top five cornerbacks will play in this preseason finale, so look closer at rookie Ephesians Prysock, veteran Darrell Luter, and second-year option Jakob Robinson. At safety, veteran Ashtyn Davis and undrafted rookie Jalen Stroman get one last shot to impress.