JACKSONVILLE – Consider this Must-Win Game No. 1.

Whether Must-Win Games Nos. 2 and 3 – and so on – follow likely will depend on what the Jaguars do against the Houston Texans at TIAA Bank Field Sunday.

That's how it works in the NFL, and that's how it's working for the Jaguars right now.

The defending AFC South champions, because of an injury-plagued offense and a defense struggling to a surprising degree, enter Sunday's game at 3-3.

And as Head Coach Doug Marrone noted this week, it's not a "good 3-3." It's a concerning 3-3 after two consecutive losses one-sided enough to shake the confidence of a team that until the last two weeks has been as confident as any franchise in the NFL.

The Jaguars' 30-14 loss to the Kansas City Chiefs in Week 5 made last week's game against the Dallas Cowboys important, and players and coaches spoke of it as such. The Jaguars lost to the Cowboys, 40-7, and the past week was expectedly filled with talk of urgency and a return to basics and fundamentals.

So, yes, Sunday's game at Houston is critical. With a victory, the Jaguars would at least share first place in the AFC South – and a lot would seem right for the Jaguars.

A loss wouldn't technically end the season, but it would mean the Jaguars being out of first place in the AFC South for the first time since the end of the 2016 season, and it would mean two home division losses. It would mean a three-game losing streak. It would mean another bleak Sunday in a season that began with high hopes. It would mean nothing good and would make the task ahead very tough.

So, yeah … consider this Must-Win Game No. 1. 

Here are 10 things the Jaguars need to do to make that happen:

1.Pressure Deshaun Watson …The Texans' quarterback is talented, but he has been mistake-prone this season. The Jaguars this season haven't had a sack/turnover game like the ones that defined Sacksonville last season. Sunday would be the time to start.

2. … but contain him, too.Quarterbacks getting outside the pocket have hurt this defense. Watson – after missing 10 games last season with a torn anterior cruciate ligament – probably won't have many designed runs, but keeping him inside the pocket is key.

3.Watch the bootlegs and rollouts.It feels like the book on the Jaguars' defense is starting to be that it can be beaten with rollouts and misdirection to neutralize the Jaguars' speed. If that's the book, the Jaguars must close it.

4.Start fast.The Jaguars have fallen behind early in all three losses this season. They have led big in all three victories. It's an obvious key to victory, but something a team must do.

5.Protect Blake Bortles.Yes, the Jaguars' fifth-year quarterback is struggling. But he has been pressured and sacked far too much in recent weeks. He's not going to win games by himself. If the Jaguars are going to win, they can't put him in situations in which he must try.

6.Get Bortles outside the pocket.Running Bortles as a staple to the offense isn't a long-term formula for success. But for the short-term? Yeah, maybe.

7.Lift the team.This offense isn't designed to have Bortles making plays without the help of a running game. So, yes: The Jaguars' running game must be better than it has been in recent weeks. But Bortles has been very good at TIAA Bank Field for the last season or so. He needs to continue to that trend Sunday.

8.Get the Texans blocked.This means blocking end J.J. Watt. And linebacker Whitney Mercilus. And linebacker Jadeveon Clowney. It's a brutally tough task for an injured offensive line that's struggling. But the NFL isn't supposed to be easy.

9.Make a play, any play.The Jaguars are injured, and a lot of the key pieces on offense entering the season are among the wounded. But someone from among those left must make a big play. Wide receivers Dede Westbrook and Keelan Cole, running back T.J. Yeldon … someone.

10.Feed. Off. The. Crowd.This game could have a last-stand feel in terms of this season's postseason hopes. It sure has a must-win feel. That homefield advantage the Jaguars worked to reestablish in the last season and a half could come into play in a big way Sunday.