PHOENIX — This winter, after a season that earned Justin Jefferson NFL Offensive Player of the Year honors, Kevin O'Connell spent hours in his office looking for multiple answers to a single question:

When teams are set on stopping Jefferson, what can the Vikings do about it?

O'Connell calls it "the JJ effect," when opponents abandon typical coverage tendencies in an all-out effort to keep the 23-year-old receiver from beating them downfield. In multiple games last season, the Vikings' pregame scouting reports would chart upcoming opponents playing man coverage a majority of the time; on game day, those same teams would keep two safeties downfield most of the time, or construct double teams to deny Jefferson the ball.

When the Rams won the Super Bowl in 2021 with O'Connell as offensive coordinator, the team sometimes responded to coverage plans for Cooper Kupp with adjustments quarterback Matthew Stafford hadn't even practiced during the week. Kirk Cousins and Jefferson did the same thing "a couple times this year for some game-winning plays," O'Connell said.

"And for that to happen in Year One is pretty remarkable, and I give our players a lot of credit — Kirk, our pass game, and how it kind of came to life," he added.

This offseason, the 14 different teams scheduled to play the Vikings this fall are devising new ways to slow Jefferson down. The Vikings are working on new things, too.

O'Connell has studied how elite receivers are being defended around the league, from teams that jam receivers at the line to ones that play man coverage with either one or two safeties deep. He said he's looking for new techniques Jefferson can use to beat defenders off the line, find space in coverage and win on jump balls, "which, by far, is the most fun part of coaching him."

The Vikings have shifted their personnel, too, signing tight end Josh Oliver to a three-year deal and bringing back running back Alexander Mattison for two years while giving fullback C.J. Ham a contract extension through 2025. They're trying to build a more efficient run game than they had in 2022, when their 38.1 success rate ranked 25th in the league, according to data from NFL Fast R.

A run game that can be more productive on early downs, O'Connell believes, will give Cousins more manageable passing downs. It could also provide the Vikings more personnel options, with opportunities to put Jefferson in matchups against a linebacker if defenses stay in base coverage against the Vikings' heavier sets.

"You feel like, if you want to have three tight ends in there, you can," O'Connell said. "If you want to play the game with five wideouts, we can. If we want to play on our terms — and I know I say that a lot — you've got to have the personnel to do that. And I feel like we do."

They will have to find another receiving option, after Adam Thielen signed a three-year deal with the Panthers following his release from Minnesota. Though Jefferson "will always be our Number One," O'Connell said, the Vikings are trying to find complementary players "who are major focal points of our offense, can win one-on-one matchups and be great with the ball in their hands after the catch."

K.J. Osborn, who caught 60 passes for 650 yards last year, could get the first shot at the No. 2 receiver role this year, and O'Connell said he's excited for players like Jalen Nailor and Jalen Reagor to play bigger roles that have them lining up in multiple receiver spots. The Vikings will have a full season with tight end T.J. Hockenson, and Oliver, who caught a career-high 14 passes last season while playing in a Ravens offense that often had him blocking for Lamar Jackson, could get more opportunities as a receiver.

There's little doubt the Vikings' opponents will again build their defensive plans around stopping Jefferson. Whether through their playbook or their personnel, the Vikings have spent a decent chunk of their offseason trying to turn the focus on Jefferson into an opportunity.

"If we can run the football more efficiently and marry the run and the pass with play-pass keepers and screens and different variations of the pass game on our terms, I think that's going to bode well for teams that want to feature so much coverage to Justin," O'Connell said. "There's so much emphasis on what he does and what we do in the pass game that we've got to take advantage of that."