Cornerback Captain Munnerlyn signed a three-year contract last March with the Vikings. He realizes if he doesn’t step up in a hurry, it could end up being a one-year deal.

Munnerlyn, one of Minnesota’s most decorated free-agent signings, knows he’s underachieved. That’s why he’s honing in on having a strong regular-season finale against Chicago on Sunday at TCF Bank Stadium.

“Just to leave the good taste in the coaches’ mouth,” Munnerlyn said. “I haven’t been playing my best football this year; I don’t think so at all. So I’m honest with myself. I know I’ve got to play better if I want to be here.”

After spending his first five years with Carolina, Munnerlyn signed a deal worth $11.25 million, with $4.45 million guaranteed. However, Munnerlyn could be released during the offseason, and it would cost the Vikings only $1 million in dead money against the salary cap over the next two years.

“If it happens, I’ll be a little upset at myself because I didn’t come out and show what I’m capable of doing,” Munnerlyn said. “I was playing a little safe this year, not taking the chances that I’m used to. … I’ve got to let them know, ‘Hey, man, let’s take another chance on this guy.’ ”

After being ranked the NFL’s 10th-best cornerback last season by Pro Football Focus, Munnerlyn is rated No. 50 this year. While he has continued to be a starter, he’s been beaten too often, including a disastrous outing Sunday when Miami quarterback Ryan Tannehill threw for 396 yards.

Munnerlyn, 26, doesn’t want to make excuses. But he said having a hamstring issue and beginning training camp on the physically unable to perform list was hardly the ideal situation.

“Being in one place for five years and coming to another place and a new environment with new teammates and new coaches … I didn’t start off right in training camp,” Munnerlyn said. “I’m on the PUP list. I never really got back to being myself like I’m capable of doing.”

Munnerlyn, though, remains optimistic. He’s hopeful of a good finish against the Bears, having had one of his better outings of the season in a 21-13 loss Nov. 16 at Chicago.

“I’ll be OK,” he said. “I’m a fighter. Everybody knows that if anybody can get out of this, it’ll be me. … I feel like I’m a good player. I just didn’t have one of them years. I feel like every athlete goes through something like this,”

Helping Munnerlyn through his tough season has been Vikings linebacker Jasper Brinkley, his former teammate and roommate at South Carolina. Brinkley can speak with experience about difficulty in switching teams, having struggled last year with Arizona after playing with Minnesota from 2009-12.

“I know Captain not only as a player but as a friend,” Brinkley said. “I know what he strives to be, and I know any time a guy says (he’s had an off-year) he knows what it takes to be where he wants to be. I’m sure that he’ll get the job done. Another year in the system, and you’re always more comfortable.”

Munnerlyn isn’t certain he will get that chance. A strong outing against the Bears could help make it a reality.

Injury report

The Vikings are in jeopardy of being without three injured starters Sunday.

Tight end Kyle Rudolph (ankle) and linebacker Chad Greenway (knee) have yet to practice this week. Linebacker Anthony Barr (knee) already has been ruled out while having remained on the 53-man roster.

The Vikings released an injury report after Thursday’s practice identical to the one sent out Wednesday. In addition to Rudolph, Greenway and Barr, wide receiver Jarius Wright (lower back) and linebacker Brandon Watts (hamstring) also didn’t practice, and haven’t all week.

Greenway hurt his knee last Sunday at Miami and returned to his native South Dakota for Tuesday’s funeral of his father, who died last week. Rudolph could miss his second straight game and eighth of the season.

Follow Chris Tomasson at twitter.com/christomasson.