NASHVILLE, Tenn. — It all started at a local high school back in 2021, when 49ers star George Kittle — with his famous friends Travis Kelce and Greg Olsen — launched an event called “Tight End University.” That first year felt less like a truly organized operation and more like a group of big dudes gathering for a summer football outing in the park.

Fast-forward to this week. Tight End U, the annual summit designed to promote what had been one of the sport’s relatively unheralded position groups, met at Vanderbilt University for its sixth installment. It’s now a heavily sponsored, in-stadium extravaganza featuring more than 90 NFL players and several celebrities — including one of the world’s biggest stars.

To close the event, Taylor Swift, Kelce’s fiancée, took to the stage for a big-ticket wrap-up concert.

Swift then performed “Love Story,” much to the delight of Kittle, his wife, Claire, and nearly 5,000 Tight Ends and Friends (that was the concert’s official name) at the overflowing venue.

Yup, Tight End U has come a long way since its modest start.

Olsen, standing on the FirstBank Stadium field during the actual football portion of Tight End U, a few hours before the concert, marveled at the growth.

Did he ever think Tight End U could get this big?

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“No,” Olsen said incredulously, as he whipped out his iPhone to shoot a panoramic video of the throngs of fans in the stands. “This is wild. They’re here to watch guys practice.”

That workout was newsworthy, especially because it featured two prominent 49ers returning to the field. Here’s a rundown of the day.

• To the surprise of many, Kittle — who tore his Achilles in January — participated in early activation drills. He looked to be moving well and is shooting to return for the 49ers’ season opener Sept. 11 against the Los Angeles Rams in Australia.

“Definitely on track,” Kittle said. “I have a chance. Nothing’s 100% certain, but I haven’t taken a step back. Nothing bad has happened. Knock on so much wood. We’re slowly getting better. That’s all I can ask for. We’re pushing as hard as we can without being an idiot.”

• Backup quarterback Mac Jones might’ve stolen the show with his gregarious antics. And Jones — who was sidelined with a sore shoulder during the 49ers’ spring program — threw passes during Tuesday’s session.

Tight End U ended up being a convention of 49ers quarterbacks past and present. Starter Brock Purdy, whom Kittle had been recruiting for the event since 2023, finally attended, as did former backups C.J. Beathard, Nick Mullens, and Brandon Allen.

Purdy moved to the Nashville area last offseason, so he and Kittle’s home bases are close.

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“I think that was a huge reason we came out here,” Purdy said. “Obviously George, but also the hub of guys that he’s built up by training at his barn and out on his field. And specifically throwing to him — he’s my tight end. So for us to have that chemistry all offseason, heading into camp, we’re hitting it off well.”

Purdy said he plans to convene with other 49ers for throwing sessions over the next month before veterans report to training camp July 25. The team has three prominent new receivers: Mike Evans, Christian Kirk, and rookie De’Zhaun Stribling.

“I think Brock’s done a great job this offseason building with the new guys,” Jones said. “Mike Evans, Stribling. We know we have great coaches and players. We’ve just got to be healthy. But we know that if not, we’ll figure it out.”

• Another first-time attendee was fullback Kyle Juszczyk, the longest-tenured 49ers player. Juszczyk signed as a free agent in March 2017; Kittle joined him as a draftee the following month. Now good friends, they’re entering their 10th seasons with the 49ers.

The versatile Juszczyk actually took more snaps from a tight end alignment than he did from fullback last season, highlighting the interchangeability of the 49ers’ offense.

“There’s so much overlap between what I do and what tight ends do, so it only makes sense,” Juszczyk said. “Now it’s gotten to the point where, for all of OTAs, I met with the tight ends. I can learn from what they’re being taught. They can learn from what I’m being taught from the running back room. It really is merging world.”

• This was the first year that Tight End U was open to the general public. Tickets were free, and hundreds of fans lined up hours before gates opened on Vanderbilt’s campus. Many wore 49ers jerseys — one family even reported making a five-plus-hour drive from West Virginia to see Kittle and Co. in person.