The Buffalo Bills open 2020 NFL training camp on July 28 in Orchard Park, New York. Here's a closer look at a few storylines:

How big of an impact will receiver Stefon Diggs have on an offense that ranked in the bottom third in most passing categories?

Diggs might represent the single-biggest impact of any skill player who joined a new team this offseason -- and yes, that includes receiver DeAndre Hopkins in Arizona. The Bills' passing offense has been below average the past two seasons, although it showed signs of life in 2019. Quarterback Josh Allen showed he could make things happen last season with a proper supporting cast and now gets a bonafide No. 1 target to pair with last year's 1,000-yard receiver John Brown. Diggs, 26, is a player who can score any time he touches the ball and will command defenses' attention, both of which are qualities Buffalo desperately needed.

Allen has finished last among qualified quarterbacks in completion percentage each of his first two seasons. What does he need to show this year to prove he is Buffalo's franchise QB?

Allen needs to demonstrate an ability to take calculated risks in 2020 -- specifically when to be a hero, when to trust his teammates to make plays and when to simply live to fight another play. He may never be one of the league's most accurate passers, but now that he's in his third season, his processing time should speed up and timing shouldn't be an issue on many of his misses. Allen's arm strength is one of his trademark skills, but he struggled to complete passes downfield in 2019; that will need to change this season as the Bills hope to bring their offense on par with their stellar defense.

With 10 defensive starters returning and depth at every position, is it realistic for the Bills to finish as a top-three defense for the third consecutive season?

At this point, a top-three defense is an expectation in Buffalo. Its strength lies in its secondary, where All-Pro cornerback Tre'Davious White returns along with safeties Micah Hyde and Jordan Poyer. Pro Bowl linebacker Tremaine Edmunds has emerged as one of the better players at his position and tackle Ed Oliver anchors a defensive line that added Mario Addison, Quinton Jefferson and A.J. Epenesa. This season will prove just how good Leslie Frazier's defense is as the Bills face explosive offenses in teams from Kansas City, Arizona, Seattle and San Francisco -- all in a seven-week span.

The Bills believe Devin Singletary could be a workhorse running back, but also drafted Zack Moss in the third round. How will one of the NFL's youngest tandems split carries in 2020?

Conventional thinking says the hot hand will get the most carries, but Singletary should dominate snaps early in the season. He finished with 15 fewer carries than Frank Gore last season after missing four games, but out-touched the veteran 131-65 from Week 9 through Week 16. Until Moss proves he deserves a larger share, expect a similar split in backfield duties in 2020 with Moss handling short-yardage and goal line work. Singletary is talented enough to be a three-down back, but the Bills would prefer not to completely wear out the 2019 third-round pick.

Buffalo signed Josh Norman during the offseason, reuniting the cornerback with his former defensive coordinator Sean McDermott. How realistic is a return to that All-Pro form for Norman?

The main thing to remember regarding the addition of Norman is that, unlike his situation in Washington, he was not signed to be the Bills' top cornerback. After experiencing three position coaches in four years, Norman returns to a zone-heavy scheme similar to the one he played in during his All-Pro campaign in Carolina in 2015. The talent around him and tempered expectations should allow Norman to succeed in Buffalo, where cast-off veterans seem to thrive when given a second chance.