JACKSONVILLE – We turn now to the veteran newcomers.

And as the Jaguars enter the 2015 season, they not only have plenty of such players, they are counting on several veterans who joined the team during the offseason to play critical roles.

That's not always ideal. Conventional wisdom tells you the best way to build an NFL roster is through the draft, and David Caldwell – the Jaguars' third-year general manager – would be the first to tell you he agrees with that wisdom.

But when Caldwell took over as general manager in 2012, he also laid out a plan through which the Jaguars would build through the draft and start significantly supplementing with free agents in the third year of the team's building process.

This offseason, Caldwell and the Jaguars absolutely stuck to that plan, with the result being a starting lineup that could feature at least six veteran newcomers.

That's more than 25 percent of the roster, and that makes this free-agent class one of the most important in the franchise's 21-year history. On paper, it's a group that appears to have a very real chance to represent a significant upgrade.

With that in mind, here are five Jaguars free agents to watch when training camp opens at the Florida Blue Health and Wellness practice fields on July 31:

1.Julius Thomas.The veteran tight end gets the top spot on this list, and deservedly so. He not only was the Jaguars' most high-profile free agent signing this offseason, he perhaps is as high-profile a free agent as the team has had in more than a decade. Thomas caught 12 touchdown passes with Denver in each of the last two seasons and made the Pro Bowl following each season. He stood out in the Jaguars' offseason program immediately, showing athleticism, speed and pass-catching ability the team hasn't had at the tight-end position in recent memory. It's perhaps not fair to expect Thomas to match the production he had with Peyton Manning in Denver, but it's also hard to imagine him not being a significant big-play and red-zone upgrade.

2.Jermey Parnell/Stefen Wisniewski.This is cheating a bit, but we'll link these guys together. That's because together they have the potential to strengthen and deepen on offensive line that very much needed strengthening and deepening. While it's difficult to judge offensive linemen in non-padded work, Parnell – who started five games for Dallas last season – appeared in the offseason to be a significant upgrade at the right tackle position. Wisniewski, a starting center with Oakland in his first four NFL seasons, was limited in the offseason with a shoulder injury. There's no guarantee he will beat out second-year veteran Luke Bowanko for the starting job, but Wisniewski's addition adds depth and competition to an interior that suddenly looks significantly better than last season.

3.Jared Odrick.As is the case with offensive linemen, it's difficult to evaluate defensive linemen in non-padded offseason work. Which is why Odrick is a key player to watch once the pads go in midway through the first week of training camp. The Jaguars signed him in the first wave of free agency from the Miami Dolphins, and he'll enter camp starting at the strong-side defensive end position that Red Bryant played last season. Odrick is expected to bring a more penetrating, athletic style to the position; that could help the spot generate more pass rush than last season. His addition is one reason to be optimistic the defense can improve despite the loss of first-round pass rusher Dante Fowler Jr. for the season.

4.Dan Skuta.Skuta wasn't the most high-profile of the Jaguars' first-wave free-agency signings, but there's an enormous respect for Skuta among Jaguars veterans. He's a veteran, stout presence against the run and produced in an extensive pass-rushing role for the San Francisco 49ers last season. He's considered an ideal fit for the Jaguars' Otto position, and along with Odrick should give the Jaguars a significantly more formidable strong-side defensive presence against the run.

5.Davon House/Sergio Brown.The Jaguars felt good about the young players in their secondary already. They felt better after signing House and Brown as free agents. House, who started 14 games for Green Bay over the last three seasons, has the size and athleticism to play press coverage in head coach Gus Bradley's system. Combined with the return of Demetrius McCray, Aaron Colvin and Dwayne Gratz, the addition of House gives the Jaguars four young cornerbacks to compete and add depth to the outside corner and nickel positions. McCray and House will enter training camp as the starters, but watch for competition in camp. Brown's addition gave the Jaguars a veteran option at free safety. An unrestricted free agent from Indianapolis, his hold on the starting position grew stronger with a broken arm sustained by rookie James Sample in organized team activities. Whatever Brown's eventual role in the secondary, he's a solid special teams player who adds experience and depth to the safety position.