The Houston Texans went 4-12 last season and were one of the NFL's worst teams. But coach Bill O'Brien went 9-7 in each of his first three years with the franchise, including two playoff appearances. And there's every reason to think that the 2018 version of this team could not only be O'Brien's best, but the AFC South champions and perhaps one of the league's biggest surprises.

What happened last year

Twelve months ago, the biggest storyline in Houston was whether then-rookie Deshaun Watson would earn the Texans' starting job. The team had traded up in the first round to draft him, but despite an impressive preseason, O'Brien announced (almost exactly a year ago to the day) that veteran Tom Savage, who had two career starts, would be the No. 1 quarterback.

"Deshaun is a very, very good young player who has a bright future in this league," O'Brien said at the time. "Let's put the cards on the table, but Tom has been here for four years. The way we want to play, the style relative to getting guys lined up, protection points, route reads, putting guys in the right spots, Tom's ahead of Deshaun."

That lasted a whopping 30 minutes. Watson replaced Savage after one half of uninspiring football; the Texans trailed the Jaguars 19-0, Savage was just 7 of 13 for 62 yards with two turnovers, and O'Brien had nothing to lose by turning things over to the rookie.

Watson finished 12 of 23 for 102 yards with a touchdown, an interception and a lost fumble. Far from flawless, sure, but the flash of talent was enough to convince O'Brien that he had found his starting quarterback. Watson started the next six games, and led the Texans to a 3-3 mark over that span that included five multi-touchdown games (including four against the Titans in Week 4, five against the Chiefs in Week 5, and four more against the Seahawks in Week 8, which was Watson's last game of the season before he suffered a torn ACL during an early November practice).

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For an idea of just how remarkable Watson was in less than a half a season of work, consider this: He ranked 14th among all quarterbacks in total value, Football Outsiders' cumulative measurement of success. And in terms of value per play, Watson was 7th, just behind Carson Wentz and just ahead of Ben Roethlisberger.

Then there was his Week 8 performance against the Seahawks. When it was over, Watson was 19 of 32 for 402 yards, 4 touchdowns, 3 interceptions and a 106.9 passer rating in a game the Texans lost, 41-38.

Here's Watson's first touchdown throw of the game:

It got better from there:

When it was over, then-Seahawks cornerback Richard Sherman, who isn't easily impressed, couldn't quit talking about Watson.

"You played the best game any quarterback has ever played against us, and we've played all the legends. I respect how you hung in there and kept battling and battling," Sherman told's Peter King after the game.

"My God, Houston's so lucky," Sherman continued. "By next year he's going to be a top-five quarterback in this league, and that includes the two big dogs [Tom Brady and Aaron Rodgers]. He makes you dig to the deepest part of your competitive juices to beat him."

Days later, Watson tore his ACL, but now, more than nine months after the injury, he appears on track to proving Sherman right.

The Texans were 3-4 when Watson went down. Over the final nine games of the season, with Savage and T.J. Yates as starters, the team went 1-8. It gets worse; with Watson, the offense averaged 34.7 points a game. Without him, the offense averaged 13.7 points. Just so we're clear, that's three fewer touchdowns a game. That's a huge problem under most circumstances, but it was exacerbated in Houston because three weeks before Watson went down, J.J. Watt and Whitney Mercilus were lost to season-ending injuries. And the defense, which ranked 9th in efficiency in 2016, dropped to 23rd last season. Put another way: That's how a team manages a single win over its final nine games.

Why this season will be different

The simple answer: The team's best players are healthy, starting with Watson, Watt and Mercilus. But this is football. Guys get hurt, often for long stretches, and roster depth determines whether a season is a success or failure. A year ago, bad luck -- 13 started ended up on injured reserve -- and lack of depth, particularly at quarterback and in the heart of the defense, led to four wins, and last place in the AFC South after the Texans had won back-to-back division titles in 2015 and 2016. On paper, the Texans are better now than they were a year ago. With a little luck in keeping players healthy, they should go from worst to first in the AFC South and capture their third division title in four seasons.

It all starts with Watson, and the preseason hype is well-deserved, but he can't do it alone.

DeAndre Hopkins: How good is Hopkins? He had 96 catches for 1,378 yards and 13 touchdowns last season, including three 100-plus-yard games after Watson's injury. Hopkins ranked 4th in total value among all wideouts, behind only Antonio Brown, Marvin Jones and Keenan Allen. We can't imagine what type of numbers he'll put up catching passes from Watson over an entire season.

Will Fuller: There are few people on planet as fast as Fuller, a fact that was on full display during a four-game stretch last season when he hauled in 13 passes for 279 receiving yards (21.5 YPC) and a whopping seven touchdowns. Here's Fuller against the Chiefs in Week 5 last season:

And you can see all seven touchdown grabs right here.

Bruce Ellington: One of 20 Texans' players to end up on IR a year ago, Ellington had 29 catches for 330 yards and two scores in 11 games. He looked sharp in the team's Week 2 preseason win over the 49ers, hauling in three passes for 44 yards -- including a 1-yard touchdown on fourth down. 

There's a good chance Ellington moves ahead of Braxton Miller on the depth chart but the overarching points remain: The more speed the Texans have at wide receiver -- where veteran Sammie Coates and rookie Keke Coutee are also burners -- the harder it will be for defenses to double-team Hopkins.

THE RUNNING BACKS: The Texans' running game ranked 21st last season but that was due in part to the loss of Watson, which made the offense one-dimensional. Lamar Miller led the team with 888 rushing yards (3.7 YPC) but ranked 25th in value per play, according to Football Outsiders. D'Onta Foreman ran for 237 yards (4.2 YPC) and Alfred Blue had 262 yards (3.7YPC). The Texans player with the highest average yards per carry and the team's third-leading rusher? Watson, of course (269 yards, 7.5 YPC).

And while Houston doesn't have a dynamic running back, O'Brien won't abandon a balanced offense because of it. This will make it more difficult for opponents to focus on Watson and his big-play-threat receivers -- that said, both Miller and Foreman are solid pass-catching backs -- though Watson's athleticism could mean more read-options.

THE OFFENSIVE LINE: Here's the group that could make or break the Texans' season. In 2017, the O-line ranked 20th in run blocking and 30th in pass blocking. Worth reiterating: Houston won four games. In 2015 and 2016, when the team won the division, the O-linemen were replacement-level or better.

So the good news is that this unit doesn't need to be among the league's best, they just need to be average, which would be a marked uptick from last season's abysmal performance. Free-agent acquisitions include Zach Fulton and Senio Kelemete at guard and Seantrel Henderson at tackle. All are expected to be starters, along with 2017 fourth-round pick tackle Julie'n Davenport (four career starts) and center Nick Martin, who had 14 starts a season ago.

"They know who's back there," O'Brien said at the start of training camp, referring to the offensive line's No. 1 priority: protecting Watson. "They know how important that guy is to our football team, [and] they understand the importance of what their job is."

Fulton added: "He's a key piece to our offense. We definitely want to keep the quarterback as healthy as possible. We don't want anybody to touch him. So you've got to take pride in that as offensive linemen."

And threw two preseason games and 67 pass attempts, the Texans have allowed exactly zero sacks. Yes, defenses aren't doing anything exotic this time of year but it's a good start for an outfit that gave up 54 sacks last season.

ROMEO CRENNEL AND THE DEFENSE: Crennel returns to defensive coordinator after helping Mike Vrabel in that role last season when injuries and inconsistency saw the Texans defense slip to 23rd overall (25th against the pass, 12th against the run). From 2014-2016 under Crennel, Houston's defense ranked 6th, 8th and 9th, according to Football Outsiders. 

The expectation is that they'll again be a top-10 unit, thanks in part to having Watt and Mercilus healthy, but also because of names like Jadeveon Clowney (who will benefit from Watt's return perhaps more than anyone), free-agent acquisition safety Tyrann Mathieu (who covers like a cornerback), former first-rounder cornerback Kevin Johnson (who can shadow opponents' top receivers), athletic young linebacker Zach Cunningham (who is a sideline-to-sideline player) and third-round pick Justin Reid (who led the team in tackles in their Week 2 preseason game).

What about the rest of the division?

The Jaguars are the preseason favorites, and rightfully so after going 10-6 last season and making it all the way to the AFC Championship Game. But this team is only as good as its quarterback and there's no guarantee that Blake Bortles can improve on his replacement-level 2017 campaign after struggling through the first three years of his career. And if the Jags' defense, which was dominant last season, isn't nearly so in 2018, that puts more pressure on the offense to score points. 

Mike Vrabel is the new coach in Tennessee, a team that went 9-7 a season ago but should have been much better. At issue: Marcus Mariota's consistency, something that has been lacking in his three NFL seasons. If he can put it together from one week to the next, the Titans could be really, really good. As a rookie, Mariota was 20th in value per play among all quarterbacks. He improved to 10th in 2016 but fell to 28th last year when his touchdown ratio slipped from 2.9/1 to 0.9/1. Put another way: As long as Mariota is up and down, the Titans will continue to hover around .500.

The Colts are one of the league's most intriguing teams, but only if Andrew Luck returns to his Pro Bowl form. He didn't see the field last season because of a nagging shoulder injury and after progressing slowly this offseason, he's showed glimpses of his old self during limited preseason action. But it's easy to imagine that Luck will need some time to knock the rust off, and this assumes that his offensive line is good enough to keep him upright. A lot of things have to go right in Indianapolis before the Colts work their way back into the playoff conversation.