Vikings coach Mike Zimmer wouldn't give a specific timetable for tight end Irv Smith Jr.'s recovery from knee surgery but acknowledged the team is preparing as if he will miss the entire 2021 season after having knee surgery Wednesday to repair his meniscus.

"We knew [before the surgery] that it was probably going to be a little while anyway," Zimmer said. "So, yeah, those are all part of the things you plan for. … That's kind of how it goes."

Zimmer said the 23-year-old Smith and the Vikings opted to repair the meniscus rather than remove it. A full repair typically takes four to five months or longer to recover from while a removal requires a much shorter recovery. The Vikings put Smith on injured reserve Wednesday.

"They repaired the meniscus, which is the best thing for him for his longevity," Zimmer said. "If they would have took the meniscus out – and I'm not a doctor or a trainer – he would have had an arthritic knee. His career would have been shortened."

Smith was injured at some point during the 11 snaps he played in the preseason finale at Kansas City on Friday. The third-year player with 90 catches for 676 yards and seven touchdowns talked just last week about how confident he was that this would be a breakout season as he moved to the No. 1 tight end spot after longtime Viking Kyle Rudolph left.

"Irv's a great football player," quarterback Kirk Cousins said. "There was no reason to think he wasn't going to have a great season."

The Vikings have four tight ends on the roster: Tyler Conklin; Brandon Dillon; former Jet Chris Herndon, acquired in a trade Tuesday; and Ben Ellefson, a Hawley, Minn., native and former North Dakota State player, who was claimed off waivers from the Jaguars.

No one in that foursome has had more than 39 catches or four touchdowns in a season.

"[Smith] was doing a lot of nice things for us that would have helped us offensively," Zimmer said. "We were planning to use Irv a little bit more on third downs as the slot receiver. We probably won't do that now. We'll probably go with three [wide receivers]. So some of those things we'll have to adapt and change."

Herndon, a 6-4, 253-pound fourth-rounder of the Jets in 2018, comes to the Vikings with 71 career catches for 796 yards and seven touchdowns.

"He was kind of a guy who's pretty good in most areas," Zimmer said. "Decent blocker. Pretty good hands. Runs decent. So, of all the tight ends we looked at, we thought he was the best option."

Cousins said Herndon should be able to help the offense relatively quickly.

"He's been in the league awhile so there's a level of just understanding what it takes no matter what team you're on," Cousins said. "There's a large part of it that's plug and play. You're ready to go. And, obviously, there's a lot to learn, too.

"I feel really good about our options [at No. 2 tight end or No. 3 receiver]. There are certainly a variety of ways you can pivot. … It could change week to week, too, just based on what we feel is our best option against that defense, against that look. It's probably a pretty fluid situation."