IRVINE, Calif. -- Josh Reynolds ran short sprints between the two practice fields at UC Irvine. Mike Thomas caught passes from punter Johnny Hekker in the end zone. Tavon Austin just stood there, watching while Jared Goff and the rest of the first-team offense navigated through a light, one-hour practice on Sunday afternoon. Another day went by without the three guys -- the only three guys, really -- who are expected to be vertical outside threats for the Los Angeles Rams. They were heavy on slot receivers before, but it's even more so the case now.

Thomas has been dealing with a hamstring injury, but he is nonetheless suspended for the first four regular-season games for violating the NFL's policy on performance-enhancing substances. Reynolds has a quad injury, but the 2017 fourth-round pick is still a little raw for the NFL. The one that hurts the most is Austin, who spent the entire offseason program recovering from wrist surgery and has sat out the past five practices because of a tender hamstring.

The Rams will be counting on receiver Tavon Austin to give them an explosive threat on the outside. Paul Rodriguez/Zuma Press/Icon Sportswire

"It’s a little bit of a setback," Rams coach Sean McVay said. "But the way we look at it is a setback is a setup for a comeback, and I think he has a good mindset about it."

McVay called Austin's hamstring "a day-to-day thing," something the Rams will be extra cautious about given his reliance on speed and quickness. When Austin does return, he's going to have a lot of catching up to do. The Rams are installing a completely different offense and want Austin to play a different role as an outside vertical threat, a skill set he hasn't really flashed in four prior NFL seasons.

"Tavon is a smart guy; he’s played in this league a long time," offensive coordinator Matt LaFleur said. "The thing that you’re missing out on is just getting that timing down with your quarterbacks. I think that’s kind of a big deal. But we have a lot of faith in his ability to bounce back and he’s very attentive in our meetings and when we’re out on the field, so he’s getting those mental reps."

The Rams were also without Bradley Marquez, who had been nursing a knee injury and was waived on Monday. They were so shallow on receivers recently that they were forced to sign three new ones in a span of two days last week: KD Cannon out of Baylor, C.J. Germany out of Notre Dame College and former quarterback Justin Thomas out of Georgia Tech. They now have 13 receivers on the roster, 11 of whom are first- or second-year players.

And none of them is named DeSean Jackson.

Jackson is one of the game's greatest vertical threats, and McVay benefited from his presence greatly while serving as Washington's offensive coordinator the past three years. Having a reliable downfield target who can take the top off defenses "softens coverage," McVay said, "and it eliminates you having to go 12, 15 plays down the field because of the ability to create explosives. We’re always looking for ways to create explosives."

With the Rams, McVay doesn't really have a player who can consistently beat defenses over the top. It's why his offense will probably look completely different. It was evident during Saturday's joint practice against the Los Angeles Chargers, when the vast majority of Jared Goff's completions traveled 10 yards or fewer, with a sizable amount coming after play-action rollouts. Receivers like Robert Woods, Cooper Kupp and Pharoh Cooper thrive in the short-to-intermediate passing game, as do tight ends like Tyler Higbee and Gerald Everett.

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"I know we have a lot of slot-body guys," Woods said, "but I feel like our guys can definitely roll. And if we hit them on intermediate routes throughout the whole game, something’s going to pop, because they’re going to have to step down eventually and play us honest. And that’s when we just run right by them."

Longtime defensive coordinator Wade Phillips faces off against McVay every day and will tell you his offense "creates a lot of problems." Woods believes McVay's concepts will keep defenses honest and prevent them from jumping routes.

"We do have a lot of slot guys," Cooper said, "but our offense lets everybody play every different position."

Cooper is a perfect example. He's 5-foot-11, carrying the label of a slot receiver from his collegiate days at South Carolina. But Cooper has been receiving the bulk of the first-team snaps in Austin's absence, lining up as an X and Z receiver on the outside, positions Cooper said he feels "very comfortable" playing.

"They teach it very well, so I know the concepts," Cooper added. "I plan to play a big role."

Cooper might, but given a clean bill of health, the Rams will seemingly go with Austin, Woods and Kupp on three-receiver sets. They're hoping the 5-8 Austin can be that vertical threat on the outside. Perhaps not to Jackson's level, but close enough so that opposing teams aren't stacking the box to stop running back Todd Gurley. They believe Austin's straight-line speed alone will make him a weapon downfield.

But they need to see it play out on the field.

"I know he’s anxious to get out there," McVay said. "We’ll see if he can do some of those things when he gets back out for us.”