The Buffalo Bills are returning the vast majority of key players from last season's 10-6 club that was good enough for the No. 5 seed in the AFC playoffs, and with a handful of new pieces added to the roster, the training camp competitions at certain spots will be fierce. Coach Sean McDermott has more depth at his disposal than in any of his first three seasons in Buffalo. 

And most of the Bills' free-agent signings from a few months ago have ties to McDermott's successful tenure with the Panthers, which makes things even more compelling. Let's explore the five most vital and riveting training camp competitions leading into the regular season.

1. No. 2 cornerback

The Bills will have their All-Pro cornerback Tre'Davious White on one side of the field this season, after he decided to opt in on deadline day. Across from him? No one's quite sure who that'll be right now. It's the most important and interesting training camp battle for Buffalo. 

Levi Wallace is the incumbent, basically. He had an fine rookie season in 2018 after going undrafted and began the 2019 season as the No. 2 corner. Although he broke up nine passes and snagged two picks, after a few games with uninspiring play midway through the season, Bills coaches decided to rotate Wallace and veteran Kevin Johnson -- who's now on the Browns. Wallace has to play more consistently to hang onto the job. And the Bills made a low-risk, potentially high-reward cornerback signing when Josh Norman was inked to a one-year deal in March. Of course, Norman rose to stardom in Carolina in McDermott's defense but is now 31 years old coming off a career-worst season in 2019. These two will battle it out and play a decently large role in deciding the ceiling for Buffalo's high-end defense. 

2. Second-string edge rusher

Jerry Hughes and Mario Addison will be Buffalo's top edge-rushing unit. Behind them, it's not so clear. Trent Murphy, now entering his third season with the Bills, is there, and while he's mostly been a disappointment as a free-agent acquisition, he did have five sacks in the final eight regular season games in 2019. 

His job won't be handed to him as the first rotational edge, although the unusual offseason will help Murphy start there when the season begins because his main competition is rookie A.J. Epenesa. The powerful and polished second-round pick will be moved around the defensive line, but he'll mainly rush around the outside. The long shot in this competition is last year's seventh-round pick Darryl Johnson, who shined in the preseason and plays with a nice collection of pass-rushing moves and strength at 6-6 and over 250 pounds. 

3. Starting right tackle

After it was reported starting right guard Jon Feliciano went down with injury, there was widespread speculation that 2019 second-round pick Cody Ford would have the inside track to taking over Feliciano's position while the veteran was sidelined. But then the Bills signed Brian Winters, who's started 61 games at right guard over the past five seasons -- and 79 games overall -- in his seven-year with the Jets. He's now the penciled in starter while Feliciano's out. 

That presumably keeps Ford in the right tackle battle with the elder Ty Nsekhe, who simply plays better then expected every time he's on the field -- and was better than Ford last season -- but got injured in November. While Ford is often pushed to the limit athletically as a tackle, it seems as though McDermott and GM Brandon Beane want to continue his audition at that position before moving him to right guard. And this battle presents somewhat of a conundrum for the Bills. Nsekhe is likely the steadier option, but if he wins the gig, Buffalo will have a second-year Round 2 pick on the bench. 

4. No. 4 wide receiver

This might actually be the most fascinating, fiercest competition in camp for the Bills, it's just that the winner might not be on the field or targeted very often, given the presence of Stefon Diggs, John Brown, and Cole Beasley. But there are many candidates here. Isaiah McKenzie brings his own specialty to the table, as a small, twitchy, gadget-type, and he's earned the trust of Buffalo's coaching staff with reliable -- albeit low-volume -- production when called upon over the past two seasons. 

Then there are the big boys, staring with Duke Williams. He's somewhat of a #BillsMafia folk hero who triumphantly made the team after playing in the CFL and caught a game-winning touchdown early in the season against the Titans. But after a few unproductive outings in a full-time roll, he got hurt. Williams then popped in the playoff loss to the Texans -- yet did drop a touchdown near the end of the half that would've extended the Bills' lead to 20-0. He's a large, physical rebounder who's not going to separate but will go up and get it with authority. Two rookies are candidates too. Fourth-round pick Gabriel Davis is a good-sized, dynamic deep threat who tracks it beautifully down the field. Obstacle in front of him this season? He didn't run many routes in college. And there's sixth-round selection Isaiah Hodgins, a tall, somewhat lanky, decently polished, double-move master with a large catch radius and strong hands. 

Lastly, Robert Foster needs a monster camp to, probably, even make the team. He was Josh Allen's go-to long-ball option as a rookie in 2018 but mysteriously barely played in his second NFL season, catching just three balls for 64 yards on just 20.6% of the offensive snaps. 

5. Third linebacker

This is fifth on the list because it's somewhat unimportant strictly due to the percentage of snaps Tremaine Edmunds and Matt Milano play in Buffalo's nickel-based defense -- Edmunds 94.6%, Milano 82.9% in 2019. But, it's important nonetheless for depth purposes and the fact that the Bills haven't really found a reliable "big nickel" safety just yet.

New to the mix is A.J. Klein, who has Carolina ties to McDermott and Beane from his time with the Panthers from 2013 to 2016. As a former fifth-round pick, Klein has overachieved his entire NFL career mostly due to higher-end explosiveness for a linebacker with an old-school, bulky frame. However, changing directions isn't his forte, and that lack of fluidity makes him a liability in coverage. Klein's knowledge of McDermott's scheme will be hugely beneficial. Vosean Joseph is an athletic, modern-day linebacker with elite-level flashes and practice squad lows. The Bills picked him in the fifth round last year, but he was placed on IR before the regular season. At Florida, Joseph displayed immense range and coverage chops, he just missed tackles too frequently and found himself out of position at times down the field.