ORCHARD PARK, N.Y. (WIVB) — Bills wide receiver Stefon Diggs was not in attendance at the first day of the team’s mandatory minicamp, head coach Sean McDermott announced during a Tuesday press conference.

“Very concerned,” McDermott said when asked about Diggs’ absence, but declined to go any further.

The Bills’ star wide receiver was at the team facility Tuesday morning but departed before the start of practice, a team representative confirmed to News 4’s Jonah Bronstein.

Diggs’ absence comes after an offseason of question marks surrounding the team’s star wideout. He was visually upset on the sideline toward the end of Buffalo’s playoff loss to the Cincinnati Bengals this past season, in which TV cameras caught Diggs making animated raised-arm gestures at quarterback Josh Allen on the sideline.

The 29-year-old also did not attend any of the team’s voluntary workouts in previous weeks.

“Internally, we’re working on some things, not football-related — but Stef, he’s my guy, I f***ing love him,” Bills quarterback Josh Allen said post-practice. “We wish he was in here today and was out there on the field with us, but that’s not the case. I’ve got his back no matter what, I’ve got no doubts we will figure out what’s going on.”

Diggs’ agent Adisa Bakari reportedly told ESPN that the wide receiver “will be there for the entire minicamp,” and that he arrived in Buffalo on Monday morning, took a pre-minicamp physical and met with McDermott and general manager Brandon Beane.

Diggs has not commented publicly regarding his reasons for staying away, but has posted various notes on social media over the past few months.

Diggs is entering his fourth season in Buffalo, and last summer was rewarded with a four-year, $96 million contract that kicks in this season.

“It’s really not that serious,” Bills pass rusher Von Miller said. “Everything will be good. I know it’s a hot topic right now — just trust me on this one, it’s not that serious. Everything will get worked out.”

Beyond Diggs, McDermott confirmed that every other player on the roster was accounted for at minicamp.

Buffalo’s mandatory minicamp runs from June 13-15 and is the first required offseason practice for all players on the roster. If a player opts to not show up, it can result in a fine of $16,459 for the first missed practice, $32,920 for the second and $49,374 for the third, according to OverTheCap.

You can view McDermott’s full pre-minicamp press conference here:

You can view Josh Allen and Von Miller’s full press conferences after practice here:

The Associated Press contributed to this report.