EAGAN, Minn. — The Vikings defense has built a reputation of being one of the league's top units in the past half-decade under Vikings Head Coach Mike Zimmer.

Minnesota brought back almost every key piece from a historic 2017 season when the unit lead the NFL in both points and yards allowed per game and also finished with the NFL's top third-down defense since the league began tracking the stat in 1991.

The Vikings defense consisted of All-Pro and Pro Bowl players and had a handful of depth players rise into key roles. The unit showed flashes of past dominance.

Minnesota finished tied for third in the league with 50 sacks, thanks in part to a whopping 19 combined sacks in home wins over the Lions (10 sacks) in Week 9 and the Dolphins in Week 15 (nine sacks), respectively.

But the Vikings also struggled at times, particularly early in the season as Minnesota got off to a 1-2-1 start.

Minnesota finished ninth overall in points allowed at 21.3 per game, but 43 of the 340 total allowed by the Vikings in 2018 came because of defensive touchdowns and a punt block by opponents.

The Vikings ranked fourth in yards allowed with 309.7 per game, marking the third consecutive season Minnesota finished in the top four in that category.

Yet after a season in which the Vikings finished 8-7-1 and missed the playoffs after lofty preseason expectations, Zimmer's defense will likely be hungry to prove once again they are one of the league's elite units in 2019.

Here are three strong defensive stats in 2018:

1. 3rd down defense

It was another banner season for the Vikings on third down, as Zimmer often dialed up pressure, schemes and disguises that left opponents flustered as they trudged off the field to punt.

Minnesota once again led the league with an allowed third-down percentage of 30.5, as opponents converted on just 58 of 190 total plays on that down. (This came a year after the Vikings set an NFL record with a third-down rate of 25.2 percent, as they allowed just 51 conversions on 202 third-downs).

Zimmer routinely credits his players for making plays when it counts, but it also helps that Zimmer can use them in a variety of looks to throw off opposing quarterbacks.

The Vikings were especially stingy on third-and-long in 2018. Opponents ran 64 total plays on third-and-9 or longer, but converted on just four of them for a success rate of just 6.25 percent.

2. Touchdown passes allowed

There was also another category where the Vikings led the league for the second straight season.

Minnesota gave up a league-low 15 touchdown passes in 2018, a year after allowing a league-best 13 touchdown passes in 2017.

The Vikings have surrendered just 28 total touchdown passes in two seasons, which is quite an impressive feat in today's pass-happy league. Especially when you consider that 19 NFL teams have allowed 28 or more touchdowns in either of the past two years.

Opponents' touchdown passes were almost evenly distributed between short, intermediate and long. The Vikings allowed four scores inside 10 yards and five between 11 and 20 yards. A half-dozen were 21 or more yards, including three in a loss to the Rams in Week 4.

3. Red-zone defense

Another year, another top three performance for the Vikings defense in the red zone.

Minnesota once again finished third in red-zone defense, holding opponents to touchdowns on 44.90 percent (22 touchdowns on 49 tries) of their trips inside the 20-yard line. The Vikings also finished third in 2017 at an event 40 percent.

The Vikings defense started off the year strong as they held San Francisco and Green Bay to two combined touchdowns on nine trips in the red zone.

But there were some struggles, most notably in the season finale when Chicago scored on all three of its red-zone possessions.

If the Vikings would have limited one of those Bears possessions to a field goal or no points, Minnesota would have finished with the NFL's best red-zone defense.

Here are two stats that need to improve in 2019:

1. Interceptions

The Vikings finished in the middle of the pack in this category, ranking tied for 18th in the league with 12 total interceptions.

But Minnesota was streaky at times by taking the ball away from opposing quarterbacks. The Vikings had eight interceptions in the first eight games of the season, with that number highlighted by a pair of three-interception games against the 49ers and Jets.

The Vikings saw plenty of upper-echelon quarterbacks as eight of their games were against the likes of Aaron Rodgers, Matthew Stafford, Jared Goff, Drew Brees, Tom Brady and Russell Wilson. Minnesota snagged three picks in those games, with one each against Brees, Brady and Wilson.

After Harrison Smith, Andrew Sendejo, Xavier Rhodes, Trae Waynes and Mackensie Alexander accounted for a dozen picks in 2017, the group totaled just five interceptions in 2018.

Chicago won the NFC North on the strength of its defense and a league-high 27 interceptions.

It wasn't all bad though, as both Green Bay and Detroit finished with seven total interceptions apiece. The 49ers ranked last with two total picks all season.

2. Rushing yards per game

The Vikings had steadily climbed in rushing defense in Zimmer's first four seasons in Minnesota, eventually reaching the No. 2 spot in 2017. Here is how the Vikings fared in recent years in terms of rushing yards allowed per game:

2014: 121.4

2015: 109.3

2016: 106.9

2017: 83.6

Minnesota took a step back in 2018 as its defense allowed 113.4 rushing yards per game, a drop off of more than 30 yards from the previous season.

And when opponents had a big day on the ground, it rarely worked in the Vikings favor, as Minnesota was 1-7 in eight games when it allowed 100 rushing yards or more.

Minnesota faced 76 more rushing attempts and allowed 478 more rushing yards this season than in 2017, but that was likely the byproduct of opposing teams having the lead more often in a frustrating 8-7-1 campaign.