Every single year, the three-day mandatory minicamps around the National Football League serves as the dress rehearsal to training camp. It's the only time players are told that they must be at the facilities for practice, and it's the last chance to make impressions on the coaching staff before nearly a month-and-a-half break before the start of camp.

On Tuesday, it was the first of three practices the Buffalo Bills conducted -- and all of which will be available to the media to view in full. What were the biggest takeaways from the day of work?

Seven observations from Day One of Bills mandatory minicamp:

1) Watkins takes another important step

- Last week, Sammy Watkins made a big progression as he continues to rehab his surgically repaired foot by being cleared to take part in individual activities during practice. And even though McDermott didn't announce the next notable step Watkins would take ahead of Tuesday's practice, there it was -- as clear as day -- once the team broke into 11-on-11 drills. For the first time since the second surgery to heal the foot, Watkins took a rep in team drills. The Bills limited him to only four or five snaps, but it's a welcomed sight to a Bills team that is hoping to get him back in full for training camp. After practice, I caught up with the Bills head coach about Watkins crossing another milestone off his rehab work. You can read the full Q&A here about the progress and where they go from here, but here's a snippet:

"...It was really all based off Sammy feeling good up until that point in practice. Really, the foundation was built last week with the individual period, and today he was able to put reps on top of the individual period which was good to see."

In his very first rep, Watkins had a pass thrown to him that was way out ahead, and nearly picked off by safety Micah Hyde. But it was clear to see that Watkins is making the progress the Bills hoped he would make, and now, it seems like he's in a good spot without any setbacks to this date. The Bills just have to keep Watkins at bay if he tries to push too hard to come back earlier than they believe he should -- which is just what happened last year. Today, though, was yet another encouraging sign for the Bills.

2) White continues to impress

- Much to the delight of Bills fans, rookie cornerback and first-round pick Tre'Davious White is taking to the defense quite well in his very first NFL offseason. White was all around the ball for the second week in a row whenever the quarterback targeted his assignment, and this week, even came down with an interception. White has easily been one of the most impressive Bills players on the field this offseason, though, you have to take it all with a grain of salt at this point of the NFL calendar -- considering it's very easy to be fooled by a performance during the offseason workouts. Even still, it's hard to not be intrigued by the rookie essentially taking on the starting role by storm this offseason. To this point, he's been everything they could have asked for, but now he must transition into when the game gets *a lot* tougher -- when the pads go on, and the physicality ramps up. If he holds his own and performs on the same level, the Bills might have a good one. There's still a long way to go, though.

3) Early on, Holmes separating from the pack

- You'll notice during these observations that I'll throw out the caveat that "it's early," and that should especially be noted for the wide receiver position. You remember this time last year, don't you? Dez Lewis was all the rage. He was one of the best players at his position on the field during the three-day minicamp, and many within the organization hoped he would take the necessary leap in training camp. He didn't -- instead reverting back to the form of his rookie training camp in which he struggled to catch the ball consistently, and faded to the background. With that written, of the horde of receivers that are trying to break through, Andre Holmes seems to have stood out the most. It was a slow start, fighting the ball a little bit early on, but he's settled in nicely -- and is even leading a lot of the positional reps during individual work. He's consistently worked with the first-team offense, and Sean McDermott made it known that he felt really impressed by Holmes with both his offensive and special teams work. On Tuesday, he was smooth with his hands and made a couple of tough catches during team drills. He's positioning himself to be a contender for a roster spot in 2017.

4) A competition at right guard?

- We took the right guard position for granted a bit, considering the jump that John Miller made as a starting player in his second year of starting -- but perhaps that's what happens when you assume things. Miller had been taking the majority of the first-team reps at right guard this offseason, but on Tuesday -- with Miller back to practice following a minor injury -- free agent signing Vladimir Ducasse worked in with the first-team at Miller's usual position. As for the third-year player Miller, he worked at second-team right guard for the majority of the day. When asked about it after practice, McDermott didn't offer much but did use the phrase "nothing is set in stone," which could mean we've got an under-the-radar positional battle shaping up for the summer. If so, it would make sense from the perspective that the current coaching staff and general manager did not draft Miller, so there must be a question of how well he fits the blocking scheme. It's one that Miller will get every opportunity to answer, but it also shows one thing: what McDermott said about competition throughout the roster wasn't just lip service.

5) Taylor struggles on Day 1

- Whether he was on a different page with his receivers or was just flat-out missing, Tyrod Taylor didn't have his best day to kick off the three-day minicamp. There was even one point where he missed a wide open target during team drills and showed his frustration with himself in the backfield. This was pretty similar to the performance from last week's OTA practice that the media was able to view, although there wasn't the one pretty touchdown throw to almost save the day. I wouldn't go jumping to any conclusions on Taylor because you still have to remember, he's trying to get a handle on the new offense just like all the rest of the players. It's going to take time. Although, you'd like him to hit his open targets in an offseason session. There will be plenty of time to correct it, but it was just a bit of a sluggish start for the Bills starting quarterback.

6) J. Williams getting glorious opportunity

- On Tuesday, we got a taste of what life would look like for the Buffalo Bills without LeSean McCoy in the lineup. The star running back was absent from practice due to a stomach virus, which left all of Jonathan Williams, Mike Tolbert, Cedric O'Neal, Joe Banyard, and Jordan Johnson to take the running back reps to kick off minicamp. Of that group, the first four names listed all worked in with some handoffs with the first unit during team drills -- but it appears a favorite has emerged with the coaching staff. Now, as Sean McDermott aptly pointed out on Tuesday, it's tough to evaluate running backs at this stage in full because of the lack of physicality at this time of year. However, they can analyze the players based on their knowledge of terminology, knowing their assignments, and making the correct reads -- and to McDermott -- Williams has stood out so far. McDermott said of Williams:

"He’s a second-year player and his development will be key to our success here moving forward."

On the field, I'd like him to be a bit more decisive on runs than I've seen from him at times. Too often, I've seen him take a carry and just keep running wide, rather than putting his foot in the ground, making the read, and getting up the field for yardage. There is still the chance he'll correct this as they continue to learn the playbook and the new offense, but it's still something to keep an eye on.

7) Henderson just a step slow

- Coming back from a rather painful sounding injury last week, backup offensive tackle Seantrel Henderson worked with the second unit at right tackle, and once again let up some pressures -- just as he had during some of the team's OTA practices. The culprit that got past him, like it was in mid-May, was a second-team defensive end, Max Valles. Whether it's the fact that Henderson seems a bit lighter, or maybe he just isn't as quick as he was, plays are being disrupted because of his assignment getting to the quarterback so quickly. At this point, as long as Cordy Glenn -- who found himself in a walking boot on Tuesday, mind you -- is healthy, Henderson might just be on the wrong side of the roster bubble.

Twitter: @JoeBuscaglia