After a 3-13 finish last season, the Jaguars entered the preseason looking for signs of progress from quarterback Blake Bortles as a key to improving the franchise's fortunes.

With Bortles entering his second season, as well as the addition of number of key free agents such as tight end Julius Thomas, offensive tackle Jermey Parnell and defensive lineman Jared Odrick, the Jaguars began the summer with high hopes.

Although injuries, most notably to Thomas, have taken their toll, the organization has assembled its deepest roster in the three years Gus Bradley and GM Dave Caldwell have been in charge.

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With the regular season set to kick off Thursday, here are the five most important things we learned from the Jaguars' preseason.

1. Bortles appears much improved

Jacksonville's short- and long-term futures depend in large part on Bortles' development. As a rookie last year, Bortles struggled, throwing 11 touchdowns and 17 interceptions, while posting a 69.5 passer rating. His performance in the preseason was far better, as he completed 39-of-60 passes for 461 yards and a touchdown. Bortles appears far more comfortable in new offensive coordinator Greg Olson's system than he did in Jedd Fisch's offense a year ago.

2. The offensive line looks far better

A season after giving up 71 sacks, the Jaguars brought in Parnell to play right tackle and Stefen Wisniewski to play center. Those moves, combined with the additon of new offensive line coach Doug Marrone, have the line looking in far better shape. Bortles was sacked just twice in the three preseason games he appeared in, giving reason for optimism.

3. The Julius Thomas era is off to a slow start

The Jaguars signed Thomas to a five-year, $46-million contract in free agency to serve as one of Blake Bortles' main targets. Unfortunately, Thomas injured his hand in the preseason opener and ultimately had surgery Sept. 2 to repair the damage. The Pro Bowl tight end is expected to be out at least a month, leaving the Jaguars without perhaps their most dangerous offensive weapon.

4. The pass rush may be hard to generate

First-round pick Dante Fowler Jr. was lost for the year during rookie minicamp. His replacement at the pass-rushing Leo position, Andre Branch, was injured during the preseason game against Detroit, and according to Gus Bradley will miss "significant time." In his place, the Jaguars will turn to second-year player Chris Smith as the starter, prefering to use vetern Chris Clemons primarily on passing downs. Clemons may be effective in smaller doses, but the team's ability to pressure opposing quarterbacks remains a question heading into the season.

5. Allen Robinson may be poised for a breakout year

Robinson, a second-round pick in 2014, caught 48 passes for 548 yards and two touchdowns in 10 games before going down for the season in November with a stress fracture in his foot. He enters the season as Jacksonville's No. 1 receiver and has earned praise for his work during the team's offseason program and training camp. The Jaguars haven't had a 1,000-yard receiver since 2005, but Robinson may just be the man to break the streak.