Early in the offseason, Kevin O'Connell placed a call to Titans coach Mike Vrabel, in hopes of finding a partner for joint practices in what's become the NFL's latest matchmaking frenzy.

The two coaches were teammates in 2008, O'Connell's first year in the NFL and Vrabel's last with the Patriots. O'Connell wanted to test the Vikings' revamped run game against the NFL's top-ranked run defense, while the prospect of measuring his corners against Justin Jefferson piqued Vrabel's interest. They made plans for two days of practices at the Vikings' facility in Eagan, and the NFL lined up a preseason game between the two teams at U.S. Bank Stadium to follow the practices.

"I just know the stuff he talks about," O'Connell said. "I know we're going to be able to put together some really good practices. Ultimately, when you do this, it's not just, 'Hey, we're going to joint practice' and worry about all that stuff later. It goes into the first phone call I make.

"Long before the preseason schedule comes out, I'm trying to see what's a fit from a standpoint of stadium availability for the preseason games, but the most important thing is the fit of getting good work in and being able to all have a good gauge of where we are as a team."

The Vikings' four days of joint practices — two against the Titans this week, two against the Cardinals next week — will probably be the only snaps their starters see against another team before the regular-season opener against Tampa Bay on Sept. 10. The first day of work against the Titans, then, served as a mirror that emphasized familiar strengths and weaknesses for their starters.

Tennessee's first-team defense kept the Vikings from scoring, as two-time Pro Bowl tackle Jeffery Simmons commanded the line of scrimmage while peppering the practice with trash talk. The Titans intercepted Kirk Cousins twice and Nick Mullens once, ending Cousins' two-minute drive with a Roger McCreary interception before pass rusher Rashad Weaver picked off Mullens on a tipped pass.

"No excuses, we have to find a way to move the ball and get points right there, but that's why I love this work," O'Connell said. "Different looks than we get every day from our defense, the ability to compete up front. It got kind of pushed right to that line today, but I thought it was really professional work across the board."

On defense, the Vikings used the kind of shifting formations that have frustrated quarterbacks throughout training camp to keep the Titans' top offense from scoring. The group pressured quarterback Ryan Tannehill several times, and safety Harrison Smith batted down a pass at the line of scrimmage.

The teams will work on red-zone and third-down situations on Thursday, before the Vikings are expected to rest many of their starters again in Saturday's game at U.S. Bank Stadium. Next week's practices against the Cardinals also figure to take the place of whatever playing time the starters might have traditionally seen in a preseason game.

Joint practices are becoming more popular across the NFL, and the Vikings, who didn't put many first-string players on the field for preseason games last year, seem likely to favor joint practices over game action for their starters under O'Connell and General Manager Kwesi Adofo-Mensah.

Preseason games give teams opportunities to sell tickets, and they aren't likely to disappear for that reason. The substance of those games, though, could continue to fade because coaches and front offices prefer joint practices for several reasons, like the ability to ensure starters face certain situations and the opportunity to evaluate players in particular matchups.

Perhaps most important, the joint practices mean starters aren't being tackled, and typically face reduced injury risk as a result, though Titans wide receiver Treylon Burks was helped off the field with an apparent left leg injury on Wednesday after going downfield for a Tannehill deep ball during a team period.

The Titans and Cardinals are the fourth and fifth teams the Vikings have hosted for joint practices since opening their headquarters in Eagan in 2018; the team's practice facility remains one of the NFL's largest, with plenty of space for 180 players to work on four outdoor fields, while the five-star hotel on the campus means visiting teams have comfortable accommodations nearby.

But the increased prevalence of joint sessions means the Vikings will eventually practice on the road for the first time since going to Cincinnati in 2016. If they want to have two sets of joint practices in 2024, it would almost certainly mean they'd conduct one of them on the road, given the fact they'll play two of their three preseason games away from U.S. Bank Stadium next year.

It's a cost of doing business in the modern NFL, when the appeal of joint practices to teams means they're not likely to go away.

"Just going against someone every single day, they kind of get to know your moves: what you like, how you run your routes," Jefferson said. "So to see someone else, to get a different look, it's definitely useful."