AP

Although a presumption has emerged over the past 15 years that NFL players will participate in offseason workouts, the only non-voluntary pre-training camp activity continues to be a single mandatory minicamp each year. Still, fans, media, and coaches get upset when players choose not to show up for voluntary workouts and drills. (Coaches have learned, for the most part, not to say anything publicly about it.)

Bills receiver Sammy Watkins, a first-round pick in 2014, has chosen not to show up for the start of his team’s offseason program. Via Mike Rodak of ESPN.com, Watkins has posted on social media a photo suggesting that he’s at the Harrah’s Cherokee Casino in North Carolina.

So Watkins apparently isn’t “All In” in the way the Bills envision it for 2016, via their hokey, obvious T-shirt slogan. It’s not clear why Watkins isn’t “All In.”

Coach Rex Ryan danced around the subject of player absences on Monday.

“I know we had a great turnout for [the] voluntary deal; we weren’t 100-percent for attendance, but a couple of guys gave me phone calls, all that stuff,” Ryan told reporters. “I won’t get into specifics on who was here and who wasn’t here because it is voluntary, but I’m encouraged by the turnout we have and everybody’s I think excited to get this season going.”

Ryan later was asked about whether Watkins was absent for health reasons. Ryan said, “I said I wasn’t going to talk about anybody being here or not being here.”

On one hand, players have every right to stay away. If the NFL wants to make these workouts mandatory, the league should bargain for that power — and in turn give the players something they want. On the other hand, a player rarely chooses to not rejoin his teammates for no reason at all. By bucking the clear trend, Watkins may be sending the message that something isn’t right.

If he’s not happy about his contract, there’s nothing the Bills can do about it until after the 2016 regular season. If he’s not happy about something else, the Bills would be wise to find out what it is.

Last year, Watkins complained publicly about his role in the offense. Later in the year, he endorsed public criticism, if needed.

“If I’m doing something wrong, call me out,” Watkins said in December. “If the line is doing something wrong or messing up, call them out. If the defense is doing something wrong, the defensive line, the secondary, call it out. Because at the end of the day, we’re doing it to win, not to get on somebody and make them feel bad. We’re grown men. This is our job. We get paid millions and hundreds of thousands of dollars. Forget the money. You’ve got to go out there each week and play for the guy next to you.”

Under that standard, maybe a teammate or two will be calling Watkins out, soon.