Could Sharrif Floyd's Vikings' tenure be over?

The Vikings decided a roster spot was worth more than a Sharrif Floyd return with three weeks left in the regular season.

And soon they will have to make a decision on the first-round draft pick's future with the team.

Floyd, the Vikings' top pick in the 2013 draft, was placed on injured reserve Monday because of lingering knee issues that have kept him sidelined since the Week 1 victory at Tennessee. The Vikings promoted defensive tackle Toby Johnson from the practice squad to take his place.

Coach Mike Zimmer said the move was made nearly three months after Floyd's Sept. 22 surgery because "we kept hanging around, hanging around. May need the roster spot at some point," Zimmer said.

Floyd has been inactive for 12 consecutive games following the operation on his left knee to address cartilage issues, according to Zimmer. He added that Floyd has only had the one operation done this fall. Floyd had been in and out of the Winter Park training facilities in recent months, with the team sending him to see specialists.

The Vikings had taken it easy this offseason with Floyd, who also needed a midseason surgery in 2015 to repair cartilage in his right knee. Floyd practiced with a brace on the knee throughout training camp, when he called his injuries "more annoying than anything."

Knee injuries, specifically, have undercut Floyd's potential as an NFL player and muddied his future with the Vikings.

It will cost the Vikings roughly $6.75 million to keep Floyd, 25, next season under the fifth-year option, which might be a lofty price tag considering his lengthy injury history. Only six Vikings had larger salary cap hits this season.

Zimmer withheld his evaluation of Floyd, who will have missed 20 games since 2014 by season's end.

"Yeah, I think I can assess him," Zimmer said. "I don't really want to assess him to the media. I'll assess him to Rick when we sit down and talk."

Floyd's combination of size (6-3, 311 pounds) and quickness are what made him five-star recruit out of a Philadelphia high school and coveted by NFL teams after two seasons at Florida. His knee issues first surfaced on an NFL injury report during the 2014 season, his first as a starter.

Floyd had 3½ sacks in a five-game stretch of 2014 while playing through knee and ankle injuries, but he was then shut down for much of four games. He also missed the bulk of four games last season following the midseason knee operation on his right knee.

Floyd is the latest Vikings starter to land on injured reserve, joining quarterback Teddy Bridgewater, running back Adrian Peterson, left tackle Matt Kalil and right tackle Andre Smith.

Toby Johnson, 25, made the practice squad off a solid preseason. He was undrafted last year out of Georgia. Johnson (6-4, 325 pounds) had seven combined tackles this summer, not including a pass deflection and an interception in the exhibition finale.