JACKSONVILLE – Senior writer John Oehser addresses five topics that are becoming clearer as Sunday's game between the Jaguars and Chargers approaches …

1.Dramatic improvement.There was more to the ascension of Blake Bortles into the Jaguars' starting quarterback role than it just being "his time." The rookie improved his way into the job. Bortles, who will make his first regular-season start Sunday against San Diego, said this week what many coaches and players will tell you – that he has made significant improvement since being selected No. 3 overall in the 2014 NFL Draft in May. Bortles on Wednesday called the improvement, "Huge," adding, "I told (quarterbacks coach) Frank (Scelfo) a couple of weeks ago that it was like watching two different quarterbacks. I saw a college clip and you're watching preseason film and it's like watching two different quarterbacks. That's just a tribute to all of the work I've done with Frank and extra stuff we've done together in meeting time with (offensive coordinator) Jedd (Fisch) and (backup) Chad (Henne) … learning as much possible, continuing to get better and work every day at practice."

2. This is Year One.That's the Jaguars' approach right now offensively – that particularly with Bortles starting, this is very much Year One of this offense. The Jaguars are starting two rookie offensive linemen (center Luke Bowanko and guard Brandon Linder), playing three rookie receivers (Marqise Lee when healthy, Allen Robinson and Allen Hurns) and starting a running back who signed with the team as a free agent this past offseason (Toby Gerhart). Add to that a free-agent offensive guard (Zane Beadles) and a left tackle (Luke Joeckel) with four NFL starts at the position – that's a youth movement, and now Bortles is part of it. "This year has been new because of the fact that most of the offense wasn't with us last year," Fisch said Wednesday. "So we're really in Week Four of the development of what we're trying to get done. This will help his development because Blake is stepping in early enough that he can experience a lot of things as we go and also be a part of the process rather than come in once the process is complete."

3.Looking for improvement.There are few spots on the Jaguars not in need of improvement. That's the nature of 0-3. But one area of focus this week was Beadles. The Jaguars signed Beadles from Denver in part to provide leadership for a young offensive line – and Beadles, who has 65 career starts compared to 17 for the rest of the line, has done that. "His leadership skills have been unbelievable for us," Fisch said, with Fisch and Jaguars Head Coach Gus Bradley saying Beadles needs improvement blocking one-on-one on the interior. "When the opportunity presents itself with a three-technique and he's got to block a three-technique one-on-one we're going to continue to challenge him to finish that block all the way through," Fisch said. Bradley added, "He's met a lot of our expectations and in some areas, exceeded our expectations. I do know that he's struggled at times, at times with one-on-one, when he has one-on-one opportunities. Double teams, working up to the second level, he's been good. But the one-on-one shots he gets, I know he's been beaten a couple of times and that's what he need to tighten down, but he's fully aware of it."

4.More than two reasons.The Jaguars made two lineup changes this week in an effort to improve the NFL's 32nd-ranked defense. But middle linebacker Paul Posluszny said there's more to the equation than moving Josh Evans into the starting lineup at free safety over Winston Guy, Jr., and moving J.T. Thomas into the starting Otto position over LaRoy Reynolds. "Everybody has to pick it up a level," Posluszny said. "We'll change personnel and get guys who are going to be reliable and do their job, but everybody has to play to a higher level." The consensus among the leaders of the defense and the coaches is that the overall performance of the unit must improve, and the season-long trend of one player missing an assignment or a tackle and that causing a game-breaking play, must stop. The Jaguars reduced their missed tackles last week against the Colts to around 10 after having 21 against Washington the previous week, but Bradley said that's still too high. And Posluszny said overall improvement must come fast. "Ten of 11 isn't enough," Posluszny said. "We need all guys to trust each other and be doing their job to have the whole defense work properly. When one guy isn't, quarterbacks in this league are good enough to find the open receiver. The guy we missed, the running backs, can find a hole. Everybody's too good to make mistakes like that. All 11 guys have to be on their job."

5.The excitement around the rookie is real.That's not to imply that all is well because there is a change at quarterback. The Jaguars have been outscored 119-44 this season. At the same time, Bortles certainly has added an element of excitement and hope to the early part of the season. That's particularly notable among fans, and Bradley has talked multiple times this week about other players feeding off Bortles' energy. "You heard the excitement when he came in the game last week," wide receiver Cecil Shorts III said this week. "There's a lot of excitement. Everybody's excited for the kid." Shorts said there is a tangible, on-field excitement, too. "You know the play is never over with him," he said. "He can break off a sack, break a tackle and take off and run. You have to be more aware." …