The San Francisco 49ers fell 23-17 to the Minnesota Vikings at US Bank Stadium on Sunday.

A Week 2 defeat won't define the 49ers' season, so it's important to maintain a little perspective when assessing a loss. However, there were plenty of things that cropped up in Week 2 that matter long-term if San Francisco is going to remain among the NFL's Super Bowl contenders.

Here are the things that mattered most in the 49ers' loss in Minnesota:

Jordan Mason is a workhorse

It's clear the 49ers are comfortable leaning on Mason while Christian McCaffrey is out, and it's clear Mason is up to the task. He's not as versatile as the reigning Offensive Player of the Year, but his running style is effective in San Francisco's offense. He churned out 100 yards and one touchdown on 20 carries against the Vikings. Mason is now up to 48 carries in two games, which is five more than his previous career-high for a season. Ideally the 49ers will find a player they're comfortable spelling Mason with, but he's clearly a good player who can keep their offense moving while McCaffrey is out.

De'Vondre Campbell is struggling

The 49ers might need to make a change at their Will linebacker spot. Campbell had a rough first game, then backed that up by getting caught up on blocks, getting beat in coverage, and in general not having an impact alongside Fred Warner. San Francisco's unwillingness to have an open competition at that spot during camp may come back to bite them because having a competition during a season is difficult.

Kyle Shanahan's aggressiveness

The 49ers head coach got aggressive! This is a pretty sizable development despite the results. Shanahan went for it on a fourth-and-3 at the Vikings' 25 early in the second quarter. On that same drive he went for it on a fourth-and-goal at the Vikings' 2. While they didn't score, the process was sound and the 49ers will be better if Shanahan keeps up that level of aggression early in games.

Fred Warner, game-wrecker

We may be in the midst of a Defensive Player of the Year campaign for Warner. Through two games he has an interception and three forced fumbles. His interception and first forced fumble Sunday came deep in 49ers territory and led to San Francisco touchdowns. There's a chance the Vikings win in a blowout Sunday had Warner not played the way he did.

Couldn't protect Purdy

It was a rough day for the 49ers' signal caller. He was pressured 13 times and took six sacks, both the most in Purdy's career according to ESPN's Nick Wagoner. While some of them were poor protection, he was indecisive at key moments and generally looked unsure of what he was seeing against Vikings defensive coordinator Brian Flores's defense.

Malik Mustapha debuts on defense

Starting strong safety George Odum got beat for a touchdown in the second quarter. Mustapha wound up playing the rest of the first half on defense. Odum briefly re-entered in the second half, but Mustapha stepped in and finished the game. The rookie fourth-round pick had three tackles and the Vikings didn't come up with more deep shots in the passing game. However, miscommunication in the secondary was a huge issue for the 49ers and it may be something Talanoa Hufanga's return can help remedy. It still appears Mustapha is now ahead of Odum on the depth chart.

Third-down issues

The 49ers had a third-down problem on both sides of the ball against the Vikings. They went just 2-for-10 on offense while their defense let Minnesota convert 7-of-12 opportunities. San Francisco's defense also allowed the Jets to have a ton of third-down success in Week 1. New York went 6-of-13, which means opponents have gone 13-of-25 (52 percent) on third downs vs. the 49ers this year. That's not an acceptable rate when it's five-points greater than the league-high last season.

This article originally appeared on Niners Wire: 7 things that mattered in 49ers ugly Week 2 performance