During Tuesday's coaches breakfast at the annual NFL owners meetings in Phoenix, Zimmer expressed disappointment in the way Rhodes performed last season and prioritized working with the former first-round pick to help him rebound in 2019.
"Xavier needs to play better," Zimmer said. "He needs to play better. I'm going to make sure that he plays better because those guys are important in our defense and what we do. That's going to be part of it. It's partly my job to make sure that he plays better, and I'm going to."
Rhodes, who has been tasked with shadowing opponents' No. 1 receiver for several seasons, saw a considerable dip in production. His 2018 was soured by a string of nagging injuries along with one of the worst statistical seasons of his career. Rhodes was hit with nine penalties and allowed the highest completion percentage of his career (65.2) and the second-highest passer rating (88.4) into his coverage, according to Pro Football Focus.
Zimmer, who has coached Rhodes since 2014, elaborated that the cornerback's play did not equate to the level he's reached in previous years or the amount the team is paying him. Rhodes, who signed a five-year extension in 2017 with $32.8 million in total guarantees, accounts for $13.337 million against Minnesota's cap this season.
"I just don't think he played as well as he can play and he needs to play up to his ability level and I need to make sure he does that," Zimmer said. "We're paying him a lot of money, he needs to play up to that contract."
The series of hamstring, foot and groin injuries Rhodes battled through in 2018 limited him to 14 games. The cornerback admitted to possibly "overdoing it, overworking my body" at the conclusion of the Vikings' 8-7-1 season and attributed his health issues to trying to get back onto the field too quickly.
The cornerback, who will be 29 this season, defended seven passes and notched an interception in 2018. While Rhodes is approaching an age where some cornerbacks find it difficult to maintain the speed and athleticism needed to track elite receivers, Zimmer said he doesn't see that as an issue.
"He hasn't lost speed, he hasn't lost athletic ability, he's kind of gotten away from his technique a little bit and we're going to get back to it," Zimmer said.
Still, despite Rhodes' struggles and health concerns, Zimmer is pleased overall with the status of his cornerback depth headed into 2019.
"Yeah, I think we got some good corners," he said. "I think Mike Hughes is going to be a really good player. It was really unfortunate that he got hurt. Holton Hill has a chance to be a really good player. We're always going to keep looking for corners because they get hurt and it's important in our defense that we have them. I think Mackensie [Alexander] played better last year than he's played in his three years that he's been here and that helped us a lot with the things we do. The nickelback position, those guys play 700-800 plays a game now. That was good that he played well."