JACKSONVILLE, Fla. -- The Jaguars' first-string tight end, signed in free agency, was walking around in a protective boot earlier this week and won’t play in Thursday’s preseason game against Philadelphia.

Their top rookie tight end -- whose athleticism, route-running and hands had the staff really excited about his potential in 2019 -- is two weeks into rehab of what head coach Doug Marrone said was a “significant” hamstring injury.

Two other players are also dealing with injuries, and three of the four healthy players have been with the team for less than two weeks.

Yet Jacksonville Jaguars tight ends coach Ron Middleton doesn’t talk about being snake-bit or unlucky or cursed.

“No, no, no, no. It’s part of it,” Middleton said. “I think it goes in cycles. It was just a matter of time before the tight end room [dealt with injuries] because we’ve been pretty healthy during all OTAs and thus far in camp and what not. We’ve been pretty lucky, but it’s part of it. It gives some guys some opportunity to get some reps and some work that they wouldn’t otherwise have gotten.

“Now, I would much rather have the guys that we think are going to be the ones, but just take it as an opportunity to build some depth.”

That’s certainly a look-on-the-bright-side approach, especially since he has no idea how much longer Geoff Swaim and Josh Oliver will be out. Then again, this isn’t the first time Middleton has been in this kind of situation.

Last year, top tight end Austin Seferian-Jenkins suffered a groin injury in camp and was eventually lost for the season after Week 5. Niles Paul suffered a knee injury the following week and was placed on injured reserve. James O’Shaughnessy ended up leading all Jaguars tight ends with 24 catches.

Middleton also has had to deal with injuries to his top tight ends since he arrived in 2013. Marcedes Lewis missed 13 games in 2013-14 and Julius Thomas missed 11 games in 2015-16. As a result, only one tight end has caught more than 30 passes in a single season: Thomas had 46 receptions in 2015.

This has all come during a time in the NFL when tight ends have become major factors -- and in some cases the focal point -- in the passing game. Every season since 2007 there have been at least 10 tight ends who had had 50 or more catches in a season, including a high of 20 in 2016. There were 12 last season -- the lowest total since 11 in 2008 -- but it included Philadelphia’s Zach Ertz, whose 116 catches ranked second overall in the NFL.

Pete Mitchell, Kyle Brady and Lewis (twice) are the only tight ends in franchise history to surpass 50 catches in a season.

The Jaguars are confident that Oliver, one of the team’s two third-round picks, will eventually join that list. They hoped it might be as a rookie, but that seems unlikely after Oliver got hurt on Aug. 1. The team is hoping he’ll be back in time for the Sept. 8 season opener, but Middleton said losing valuable practice time and preseason snaps will be tough for Oliver to overcome.

“The one that you would want the least to get hurt would be him,” Middleton said. “He was progressing along pretty good. Very talented. He’s taking it all in stride.

“... But hopefully he takes this time to learn the offense in and out. I know it’s no substitute for getting reps but he can be mentally prepared to the 25th power and just be ready to go once he’s healthy.”

The Jaguars signed Swaim as a free agent in March and he showed he could potentially be a reliable target in the red zone based on the way he performed throughout OTAs, minicamp and the start of camp. However, he suffered a foot injury during the Jaguars’ preseason opener and hasn’t practiced since.

Veteran Ben Koyack and rookie Charles Jones, who is the best blocker of the group, also have been battling nagging injuries but have been able to practice. O’Shaughnessy, first-year players Ethan Wolf and Donnie Ernsberger and undrafted rookie Carson Meier are the players Middleton is leaning on in practice. They are expected to play against the Eagles.

Not having experienced tight ends (other than O’Shaughnessy) or the top two options has forced offensive coordinator John DeFilippo to go with more 11 personnel (one back and one tight end) as opposed to 12 personnel (one back and two tight ends), which likely would be their base personnel.

There are still more than three weeks remaining until the season opener and Middleton hopes to get Swaim -- and possibly Oliver -- back by then, so he’s not panicking. He’s adjusting his expectations and stressing the mental part of the game.

“Meeting time is important,” Middleton said. “Once we’re on the grass we just have to be smart in individual [drills] and just keep the ones that you’ve got healthy. Don’t wear them out in individuals so you can get the team stuff done. And when you can some individual in, just specialize and stuff.

“But the meeting room is crucial now. Those guys staying abreast of what we’re doing from the playbook-wise and getting their treatment and getting ready to get back out there.”