Grant Cohn: 49ers’ multiple draft mistakes will stunt team’s development

C-plus.

You can’t give the 49ers any higher grade for their draft this weekend, even if you focus solely on the positives.

Or the positive, singular.

I’m talking BYU linebacker Fred Warner, whom the Niners drafted in Round 3. He was their best pick. Let’s start with him. You can’t say the Niners reached for Warner - he was the 70th selection. That’s exactly where he should have gone. He was a tremendous value for the 49ers.

And he addressed a need. Starting linebacker Reuben Foster could face a suspension from the NFL next season, or he could go to prison. For now, Foster is Option 1A at middle linebacker. The 49ers need a 1B.

Warner is their 1B. He can start at middle linebacker as a rookie - he’s that good. The 49ers protected themselves in case they lose Foster. Smart.

The rest of their draft wasn’t.

They passed on the highest-rated player available in Round 1 - Derwin James, the safety from Florida State. He later went to the Los Angeles Chargers, who use the same defensive scheme the 49ers use. James would have been perfect for the Niners.

But, they couldn’t take him even if they wanted. They had to draft offensive tackle Mike McGlinchey, because they had to fill a need they were about to create the following morning when they traded right tackle Trent Brown to the New England Patriots.

The 49ers didn’t upgrade by trading Brown, who has more raw talent than McGlinchey. Some consider Brown best right tackle in the NFL. Denver Broncos All-Pro outside linebacker Von Miller certainly thinks so. He called Brown the best right tackle more than once the past couple years. Even Kyle Shanahan has called Brown one of the most talented pass protectors of all time.

Brown is only 25. And yet, the 49ers gave up on him. They traded him and a fifth-round pick to the Patriots for a late third rounder. The Niners sold low.

Bill Belichick can bring out Brown’s enormous talent. You can bet the Patriots will win this trade. Belichick is not in the business of losing.

The 49ers should have kept Brown and drafted James. Trading Brown and replacing him with McGlinchey was a mistake.

In Round 2, the Niners made their biggest mistake of the draft. They traded up for Dante Pettis, a wide receiver from Washington.

The Niners didn’t have to trade up for Pettis. He probably would have been available in Round 3. And he didn’t fill a hole on the roster. The 49ers already have their starting wide receivers. Which one of the top three will Pettis beat out next season? Anyone?

Bueller?

Pettis’s best position is punt returner. He can make the first couple of guys miss, and wend his way through traffic. He’s marvelous.

But, as a receiver, he’s a tweener. He’s nowhere near as fast as Marquise Goodwin, nor is he a possession receiver like Pierre Garcon. Garcon is wide and sturdy - 6 feet, 210 pounds. Pettis is light and narrow - 6-2 195.

Pettis can line up in the slot for the 49ers and run gadget plays and jet sweeps and reverses. Cute stuff. But, so can Trent Taylor, the slot receiver the 49ers drafted last year. Taylor returns punts, too. He and Pettis have similar abilities, although Pettis probably is better.

Which means the 49ers used their second-round pick to improve marginally at slot receiver and punt returner. And they used their first-round pick to address a need they didn’t have.

That’s not going to win them the Super Bowl next season, or even the NFC West. They needed major improvements, not marginal ones.

Especially at cornerback. Starter Richard Sherman is old and slow and rehabbing two Achilles surgeries. He may not be ready for the first game or the first few weeks of the season. Or, he might play and pull up lame. Who knows?

Behind Sherman, the 49ers have Jimmie Ward, a safety they’re moving to corner. And behind him, they have another safety they’re moving to corner, Tarvarius Moore, who they just drafted in the third round.

How about a real corner?

Two excellent ones were available for the Niners when they traded up for Pettis in Round 2: Josh Jackson from Iowa and Isaiah Oliver from Colorado. Either would have been a better pick for the 49ers than Pettis.

Here’s how they used the rest of their picks:

The 49ers took an Achilles guy and two knee guys. Safety Marcell Harris tore his Achilles last July, defensive tackle Kentavius Street tore his ACL a few weeks ago and defensive tackle Jullian Taylor tore his ACL in college. Why did the 49ers pick them?

Street and Taylor are interior linemen, even though defensive tackle is the deepest position on the defense. Why did the 49ers pick them?

The 49ers took a 5-9 slot corner, D.J. Reed, who’s too short to cover the Rams’ 6-2 slot receiver Cooper Kupp, or the Cardinals’ 6-3 slot receiver Larry Fitzgerald. Moore can’t match up with the opposing slot receiver in 25 percent of the 49ers games each season. Why did the 49ers pick him?

The 49ers took a 5-10 wide receiver, Richie James, who’s now the fifth receiver on the roster shorter than 5-11. Why did the 49ers pick him?

To top it off, the 49ers did not take an outside pass-rusher. A couple would have been helpful. The Niners’ top two are Cassius Marsh and Jeremiah Attaochu, who have recorded just 16 sacks combined during their careers.

How will the 49ers sack the quarterback next season?

How has their defense gotten any better?

How can they expect to win more than eight games?

So many questions. So few answers.

Grant Cohn covers the 49ers for The Santa Rosa Press Democrat and Pressdemocrat.com. You can reach him at grantcohn@gmail.com.