LAS VEGAS -- The San Francisco 49ers just beat the Las Vegas Raiders 18-12 in the preseason finale. Here are the grades for their performance.

QUATERBACKS: C-MINUS

Mac Jones played only two series and never got into the flow of the game because his receivers weren't open (more on them in a minute). Jones finished the night completing just 1 of 5 pass attempts for yards, and his passer rating was 39.6. It would have been nice to see him play a third series just so he could get an opportunity to do something positive. Instead, the 49ers quickly yanked him for Adrian Martinez, who made some decent plays, but won't make the 53-man roster, nor should he. It's too bad the 49ers gave so much playing time during the preseason to this practice-squad quarterback who has no future on their team or in the NFL. It's also too bad that Kurtis Rourke broke three ribs running a quarterback draw near the goal line in the preseason opener. He looked good, like someone who could be Brock Purdy's main backup next year when Jones leaves.

RUNNING BACKS: A-MINUS

Jordan James made his preseason debut and gained 55 yards from scrimmage on 9 touches. He's quick, he can catch, and he runs with no hesitation. He's a good all-around backup running back. I can't believe the 49ers played Brian Robinson Jr. over him last season. That was silly. The best running back tonight was Kaelon Black, who wasn't targeted and missed a key block on one of Mac Jones' deep incomplete passes, so he still has much to prove in the passing game. But in the running game, he was a monster as usual. In this game, he gained 28 yards on 4 carries (7 yards per attempt). He clearly is the most explosive ball carrier on the team, no disrespect to Christian McCaffrey. He used to be the team's most explosive back, but now he's older.

WIDE RECEIVERS: D

They were terrible. Jordan Watkins got a chance to show something against the Raiders starters, who aren't particularly good, and he responded by catching 1 of 3 targets for 5 yards. Twice he was targeted deep, and both times he did nothing to shake the defender and get himself open. On the first deep target, Watkins didn't even bother to turn his head and find the ball. He was just out for a leisurely jog as if he already had made the team and this third preseason game was a mere formality. Watkins isn't nearly good enough to play that way -- that's why he had to stay on the field all night. Take a hint, Jordan. And he was by far the 49ers' best wide receiver in this game. None of these players run good routes. The 49ers desperately need De'Zhaun Stribling to stay healthy and produce 1,000 yards this season.

TIGHT ENDS: B

Hayden Rucci had two first downs and a touchdown catch that got called back due to a low block by Jordan James. If the 49ers keep four tight ends, which they should and probably will, then the fourth tight end should be Rucci, not Brayden Willis, who left this game early with a concussion.

OFFENSIVE LINEMEN: A

The 49ers rushed the ball well all night and took just one sack. Granted, they were facing the Raiders, who are terrible. Still, the offensive line performed well without most of their starters.

DEFENSIVE LINEMEN: C

Alfred Collins and CJ West were abysmal. Both guys repeatedly got blown off the ball in the running game. Whenever they came out, the run defense improved. Both Collins and West seem out of shape. Neither one currently can hold his ground or disengage from blocks. They're not in danger of getting released, but Collins in particular is supposed to be a starter, and they can't afford to play him right now. Their best healthy defensive lineman who played tonight is Keion White, who sacked Fernando Mendoza after bulldozing the center. In addition, backup defensive end Ogbo Okoronkwo sacked Mendoza, too. Okoronkwo absolutely has done enough to make this team.

LINEBACKERS: C

The best linebacker was Tatum Bethune, who finished with 9 tackles and an interception. Rookie Jaden Dugger played into the third quarter and recorded a team-high 10 tackles and two quarterback hits. He also missed two tackles he should have made. He's still a work in progress, and he has a ton of potential, but he's a bit of a liability as an inside linebacker off the line of scrimmage defending runs between the tackles. He seems much more comfortable as an outside linebacker on the line of scrimmage, setting edges, dropping into coverage and blitzing.

DEFENSIVE BACKS: B-PLUS

Ashtyn Davis started at safety and missed a tackle. He shouldn't make the team. Siran Neal played great at cornerback in the first half despite getting flagged for a bogus pass-interference call. Jack Jones also broke up a pass -- he does that a lot. He will start Week 1 if Renardo Green isn't back from his hamstring injury. Rookie Ephesians Prysock left this game with a shoulder injury and quickly was ruled out. That doesn't sound good.

SPECIAL TEAMS: A

Eddy Pineiro made all six of his field goal attempts, including a 59-yarder. He unironically is one of the five best players on the roster. The 49ers wouldn't have made the playoffs without him last season.