The smiles didn't last too long for the Minnesota Vikings on Sunday. After having secured two-time All-Pro safety Harrison Smith to a sizable four-year deal, they got some [more] bad news on the injury front. Irv Smith, the team's starting tight end, was set to undergo surgery to repair meniscus damage in his knee, coach Mike Zimmer confirmed on Monday. It was initially unclear what the timetable for return would be on Smith, but with the regular-season opener set to kick off for the Vikings on Sept. 12 against the Cincinnati Bengals, Smith's odds of recovering in time for that weren't promising.

Now, they're completely nonexistent. Smith has successfully come out on the other end of the procedure but will reportedly miss 4-5 months as he recovers, per Adam Schefter of ESPN. Despite the other existing firepower on the Vikings offense, this is still a blow, and especially for Smith himself.

Zimmer originally noted he didn't have details on the surgical procedure. 

"I never heard the six-to-eight-month thing," he told media. "We'll just see where it goes. A lot of times, you can't really tell on that until you get in there."

They've now been "in there", and the best-case scenario gives Smith a chance to return for the playoffs -- should the Vikings secure a seat in the postseason. The third-year talent was set to potentially have a breakout year in 2021, after being a solid rotational target for quarterback Kirk Cousins over the previous two seasons. A former second-round pick out of Alabama, Smith is a former second-team All-SEC talent who made an impact with 311 receiving yards and two touchdowns in only seven starts as a rookie. He'd up both numbers in Year 2, finishing with 365 receiving yards and five touchdowns in the same number of starts. 

With Smith likely lost for the season, the Vikings made a move to bolster the position by acquiring Chris Herndon from the Jets. Tyler Conklin, who has been out most of camp with a hamstring injury, is also in the mix.

With Zimmer looking to fully unleash him in 2021, it stands to reason Smith could do some real damage when he returns to 100 percent, and that is especially true when factoring in the presence of Adam Thielen and breakout receiving star Justin Jefferson for opposing defenses to account for.

But, for now, all he can do is heal and wait.

It's time for the Vikings to make their move in the NFC North. Can Kirk Cousins, Dalvin Cook and Justin Jefferson get the job done? Download the CBS Sports app to get the latest headlines from our team of NFL experts. If you've already downloaded the CBS Sports app, favorite the Vikings right now to get all the top headlines out of Minnesota.