Saints Panthers Football

New Orleans Saints' Alex Anzalone (47) grabs onto Carolina Panthers' Jonathan Stewart (28) as Stewart drags him upfield during the second half of an NFL football game in Charlotte, N.C., Sunday, Sept. 24, 2017. The Saints won 34-13. (AP Photo/Bob Leverone)

The New Orleans Saints were forced to place rookie linebacker Alex Anzalone on injured reserve.

Anzalone, drafted in the third round out of Florida, injured his right shoulder making a diving tackle on the third snap of Sunday's win over the Miami Dolphins in London. He left the game immediately. 

Anzalone injured the same shoulder in college and missed the better part of two full seasons. Back at Florida, Anzalone had complications from surgery to repair a torn labrum, but it's unclear if this shoulder injury is related. 

Losing Anzalone is a significant blow to a defense that played well in its past two outings.

"The other day, before he had to go out with the shoulder, he was only in for three plays, but he was going about as fast as anybody could go," linebackers coach Mike Nolan said. "The combination of his experience and the combination of his physical attributes are why he's on the field starting as a rookie."

Anzalone had 16 tackles, a sack, one tackle for loss, one quarterback hit and a pass defended in the first four games of his pro career, and he'd played 77.5 percent of the snaps in the first three games. 

"As a football player, he's mature," Nolan said. "He plays as though he's played before. Some guys come in and the NFL is more football than what they've faced in the past. In his case, he understands it well."

With Anzalone out of action, the Saints will likely turn once again to Craig Robertson, the veteran who led New Orleans in tackles last season after an injury to James Laurinaitis opened up the starter's role at middle linebacker.

Robertson has four tackles in 94 snaps on defense this season. He made 114 tackles, a sack, six tackles for loss, six quarterback hits and four pass breakups a year ago.

But the Saints' signings of A.J. Klein and Manti Te'o, plus the drafting of Anzalone, had relegated the veteran to a complementary role so far. 

With Anzalone out, New Orleans is now fairly thin at the linebacker position behind the top three players. Only Nate Stupar and newly signed Gabe Martin are available as backups — and two weeks ago, the Saints traded former first-round pick Stephone Anthony, who had some experience on the weak side, to Miami for a fifth-round pick. 

New Orleans also has former CFL star Adam Bighill on the practice squad.

It's unclear if Anzalone is a candidate to return this season.

NFL teams can bring back two players from injured reserve in a given season, and cornerback Delvin Breaux is expected to be one of those players when he returns at midseason from a stress fracture in his fibula.

Offensive line coach Dan Roushar also indicated Tuesday that right tackle Zach Strief also might be a candidate to return later in the year.

NFL teams no longer need to designate which players will return, allowing the Saints to make the decision based on how players are recovering. Any player on injured reserve must sit out for eight weeks before returning to play in a game.

The Saints filled Anzalone's spot on the roster by signing veteran defensive tackle John Hughes, according to his agent, Vincent Calo, on Wednesday.

Hughes, who spent training camp with the Saints, is part of a wave of veterans signed by New Orleans, along with Martin, fullback Zach Line and offensive lineman John Greco. 

Hughes will likely serve as a backup nose tackle to Tyeler Davison. During the preseason, the veteran made four tackles and a handful of pressures, particularly in the final preseason game against the Baltimore Ravens.

Follow Joel A. Erickson on Twitter, @JoelAErickson.