Who would have guessed that 12 weeks into this NFL season we'd be eagerly anticipating the showdown between the Los Angeles Rams' offense and the New Orleans Saints' defense -- with a possible first-round playoff bye on the line?

Last season, the Rams ranked dead last in the NFL with 262.7 yards and 14 points per game. New Orleans' defense, meanwhile, ranked 27th in yards allowed (375.4 per game) and 31st in points allowed (28.4). The Saints were even worse in both categories through the first two weeks of this season, when they started 0-2.

But now here we are, with the 8-2 Saints and 7-3 Rams being powered by the league's two most surprising units.

Here's a closer look at how they got here from ESPN NFL Nation reporters Mike Triplett and Alden Gonzalez.

Rams offense

How bad was it? Consistently bad. Almost historically bad. Heading into 2017, the Rams had suffered through a 10-year stretch during which they never once finished within the top 20 in offensive DVOA (defense-adjusted value over average). From 2008 to '15, they didn't have a single 1,000-yard receiver. The NFL produced 174 of them during that time. The Rams ranked dead last in yards after each of the past two seasons. In 2016, they also were last in points, first downs, third-down conversion rate and Total QBR. Jared Goff, their franchise quarterback, absorbed 26 sacks while starting the final seven games. Todd Gurley, one of the game's most talented running backs, managed only 885 rushing yards on 278 attempts. Their offensive line was dreadful, their receivers were underwhelming and their scheme lacked innovation. So, thoroughly bad.

Turning point: It all started Jan. 12, when the Rams trusted their gut and made Sean McVay, 30 at the time, the youngest head coach in modern NFL history. McVay worked wonders with Kirk Cousins as the Washington Redskins' offensive coordinator and was already deemed one of the game's sharpest offensive minds, somebody with a knack for making the game simple for his quarterback. But the Rams also needed to work on the roster. Andrew Whitworth, one of the game's best left tackles, replaced Greg Robinson, one of the game's worst left tackles. Veteran center John Sullivan also was brought in, solidifying the Rams' offensive line. Their receiving corps was also injected with new life. The Rams signed Robert Woods, traded for Sammy Watkins and drafted Cooper Kupp and Gerald Everett. Then, in the midst of all that, Goff got better as a second-year quarterback, mostly with his decision-making and feel for the pocket.

Where they are now: The Rams went from averaging 14 points in 2016 to averaging 30.3 points in 2017, second highest in the NFL. They could eventually join the 1965 San Francisco 49ers as the only teams to go from last to first in points from one season to the next. The Rams' increase in points per game (16.3) is on pace to be the largest year-to-year improvement since the 1970 merger. Their 303 points are their most through 10 games since 2000, which featured The Greatest Show On Turf. Goff has taken only 15 sacks. He's averaging 8.2 yards per attempt, has thrown 16 touchdowns to four interceptions and is on pace to pass for 4,176 yards. Gurley leads the NFL in scrimmage yards (1,216) and touchdowns (11). Five players (Woods, Gurley, Kupp, Watkins and second-year tight end Tyler Higbee) have caught more than 15 passes. What a difference a year makes. -- Alden Gonzalez

Saints defense

How bad was it? Historically, hideously bad. Before this season, the Saints hadn't finished higher than 27th in the NFL in yards allowed or points allowed since 2013, and, really, defense has been a problem for much of the Sean Payton-Drew Brees era. They have used five defensive coordinators since 2008, while setting the NFL record for most yards allowed in 2012 and the NFL records for most TD passes allowed and highest opponents' passer rating in 2015. Worse yet, the Saints were on pace to shatter all of those marks through two weeks this season after blowout losses to Minnesota and New England (the Saints gave up a league-high 512.5 yards per game and 388.5 passing yards per game in Weeks 1-2).

Turning point: There's a macro answer and a micro answer here. The major turning point was the Saints absolutely nailing their offseason personnel moves. They drafted cornerback Marshon Lattimore in Round 1 and safety Marcus Williams in Round 2, and signed defensive end Alex Okafor and linebackers A.J. Klein and Manti Te'o in free agency. It's easy to say the Saints "just needed a No. 1 shutdown cornerback, a quarterback of their defense at middle linebacker and a quality edge rusher opposite Cameron Jordan." But every team needs those things, and it's never easy to pull off. The Saints also overhauled their defensive coaching staff this offseason to support coordinator Dennis Allen, who has done a great job since taking over in November 2015. The more specific turning point, however, was the 34-13 victory at Carolina in Week 3, when the season was in peril after those first two ugly losses. Payton has pointed to that game (and the 20-0 win over Miami in London a week later) as the kind of confidence boost the Saints' young defense needed to prove its preseason performance was legit. "At some point, you want to see the results. And I think we saw some of the fruits of our labor," Payton said. "And you began to get a little bit of confidence after that week, and then you shut out Miami and then you start building on it."

Where they are now: Injuries have become a concern, with Okafor suffering a season-ending Achilles tear in Week 11 and Lattimore's status in doubt for Sunday's game at Los Angeles because of an ankle injury. But Lattimore, safety Kenny Vaccaro and linebacker Klein should all be healthy in time for the stretch run. And in general, the Saints have been thriving on defense since Week 3. The Saints rank third in the NFL in yards allowed and points allowed since Week 3 and second in passing defense over that stretch. Lattimore, who is the front-runner for NFL Defensive Rookie of the Year, has been the most vital newcomer. But second-year cornerback Ken Crawley also has stepped up big after being a healthy inactive the first two weeks. And that improved cornerback play has allowed the Saints' pass rush to be more effective. Jordan should be in the conversation for NFL Defensive Player of the Year with eight sacks, 15 quarterback hits, two forced fumbles, four passes defensed and an interception in the end zone for a touchdown. "These guys are growing at a rapid pace and they're making plays they hadn't made in previous years. This year they're playing lights out across the board," Jordan said of the secondary, pointing to pass breakups by Lattimore and Crawley in the end zone in Week 11. "And it's motivating and inspiring to be part of the defense. ... The passion is infectious." -- Mike Triplett