The San Francisco 49ers may have dropped their season opener against the Minnesota Vikings, but that was a tough early test for the young team. The argument could be made that the result, despite the loss, was encouraging.

Sunday's matchup was billed as a measuring stick for determining where the 49ers are in their rebuilding process. After all, many view the Vikings as one of the best teams in the league and the 49ers hung with them until late in the game.

At least, those are the thoughts of executive producer and analyst Greg Cosell, whose breakdowns can be seen weekly on ESPN's NFL Matchup show. He joined KNBR on Wednesday and discussed the 49ers' performance against the Vikings.

"You could make the argument that the Vikings are the best team in the league if you just look at their entire roster," Cosell said on the "Tobert & Lund" show. "And certainly their defense is really, really good. I'll tell you what I was impressed by — the play of the 49ers defense. I thought they played really well. I thought that they did some good things tactically. I thought some individuals played exceptionally well."

Two of those defensive individuals were rookie linebacker Fred Warner and defensive lineman DeForest Buckner. Warner's numbers immediately jump out at you, especially considering it was his first NFL game. He tallied 12 combined tackles, a pass defensed, and a forced fumble, which was recovered by the 49ers, all while playing in every defensive snap on Sunday.

Cosell cautions that numbers don't always tell the whole story. A defensive player may have a large number of tackles on the stat sheet, but you still have to look at why the player accumulated so many. Is he getting blocked? Is he having trouble getting off blocks, so he's making plays further down the field?

Warner, Cosell feels, indeed played a fantastic game and the analyst came away impressed with his performance.

"What's most interesting to me about Fred Warner, the way he was used at BYU was he was essentially a slot corner and a big safety," Cosell said. "He played outside the box probably on 90 percent of the snaps that I saw in the six or seven games that I watched in his last season there.

"And then in the preseason, I noticed he was playing stack linebacker and he flashed. Then, obviously, in this game, he played stack linebacker and played really, really well."

Cosell seemed even more impressed with Buckner's level of play against Minnesota and feels that he will one day create matchup problems for opposing offenses. Buckner had three sacks all of last season. He was credited with 2.5 against the Vikings.

"He played really, really well," Cosell said. "I thought that as a run defender, as a pass rusher, I thought he was strong throughout the game. It was a complete game for him, and it was the kind of game that they're hoping, stat-wise, he's not going to do those stats every week. Obviously, no defensive tackles does, but you want to see him play that kind of game where there's dominant elements to his play.

"And at some point then, offenses, particularly in passing situations, feel that they have to slide their protection to him and then you set up one-on-one opportunities on the other side."

Jimmy Garoppolo's performance was up and down against the highly-respected Vikings defense. The quarterback flashed during several plays, but also made costly mistakes and threw three interceptions, one of which was returned for a touchdown. Another sealed the win for Minnesota.

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"Sometimes I think he needs better vision and clarity throwing between the numbers," Cosell said of Garoppolo. "I think he has such confidence in his ability to make throws with that quick release, and he sort of snaps it off, and that's a confidence thing. So with more experience, I think that will probably subside. But he does have that tendency.

"Obviously, when you throw an interception for a touchdown, which came at the play right after (George) Kittle dropped the pass. Things like that change games. But that was a great defensive play call by Mike Zimmer and his staff. They showed blitz from one side, and the Niners reacted as such. And they came with blitz from the other side, and therefore guys got in clean."

You can listen to the entire conversation with Cosell below.