Vikings tight end Irv Smith Jr. will undergo knee surgery this week with team doctor Chris Larson after suffering a meniscus injury during Friday's preseason finale at Kansas City, coach Mike Zimmer said.

Smith's recovery timeline will be determined after the operation, according to Zimmer, who was asked whether Smith would be undergoing a meniscus trim — typically requiring a month or so recovery — or a full repair that could sideline him for six to eight months.

"I never heard the six-to-eight months thing," Zimmer said Monday. "We'll just see where he's at. A lot of times, you can't tell anything until you get in there."

Smith's injury happened sometime during his 11 snaps, in which he caught both targets for 39 yards, against the Chiefs. Smith spoke to reporters after the game with no indication he was injured.

"It's hard to know exactly what happened," Zimmer said.

With Smith, in his first year as a starter in place of the departed Kyle Rudolph, sidelined indefinitely, the team is evaluating potential additions at tight end via free agency, trades or the waiver wire as players are released around the league. All NFL teams must set an initial 53-man roster by Tuesday afternoon.

Tight end Tyler Conklin said he's "all good" for the Sept. 12 season opener at Cincinnati after returning to practice Monday from a hamstring injury that kept him out of the preseason. He becomes the presumed starter without Smith. The Vikings also have Brandon Dillon, fifth-round draft pick Zach Davidson and undrafted rookie Shane Zylstra at the position.

"It's not very good," Zimmer said of the tight end depth.

Smith's absence could impact the Vikings' approach on offense under first-year coordinator Klint Kubiak. The Vikings typically lean on multiple tight end formations, but could pivot to more three-receiver sets depending on how the 53-man roster comes together.

"We may end up being a little more three wide with some of the guys we have," Zimmer said. "All of this will shake out after the cuts. We can't jump ahead of anything right now."

Anthony Barr rode a stationary bike in the weight room while he was among 10 players held out of Monday's practice. Even though the Pro Bowl linebacker hasn't practiced in three weeks because of an undisclosed injury, Zimmer projected optimism about Barr's availability.

"I hate to say it because you guys will say I'm wrong if I'm wrong, but he's doing really good," Zimmer said. "We've got a good plan for him to get him ready to go."

Co-defensive coordinator Adam Zimmer said last week that he was unsure whether Barr would be ready to play by Sept. 12.

The Vikings also practiced Monday without Smith, tackle Christian Darrisaw, running backs Alexander Mattison and Kene Nwangwu, safeties Josh Metellus and Luther Kirk, guard Dru Samia and receivers Dan Chisena and Chad Beebe.

Beebe and Kirk are new absences after playing Friday. Kirk suffered a hamstring injury, according to a league source, and the expectation is he will be waived with an injury designation ahead of Tuesday's deadline to set the initial 53-man roster.

Ready or not?

Conklin, the fourth-year tight end, was already preparing for a bigger role as the No. 2 option. Now he's expecting to take an even bigger leap into the starting role while Smith is indefinitely sidelined.

To prepare for the top job, Conklin will draw upon last year's experience, when he was the No. 2 tight end replacing an injured Smith and then Rudolph in the second half of the season. Conklin caught 19 of 26 targets for 194 yards and a touchdown in those games.

"Sometimes, you know, you get thrown out there and you're not prepared," Conklin said. "But I think in my situation, I've got to learn from a good vet in Kyle Rudolph. I got to be eased into and basically play a starting role in the last four to six games last year, and got to have a strong offseason and feel really prepared for Week 1. So I don't think it could have worked out any better.''