Since 2016, all but three NFL teams have featured a wide receiver who has finished a season ranked within the top 32 at his position in receiving yards. The Buffalo Bills have been an exception, along with the Jacksonville Jaguars and Chicago Bears.

The last Bills wideout to place among the NFL's best 32 was Sammy Watkins, whose 1,047 yards in 2015 were 19th most among receivers.

Watkins, often injured, fell short of his potential after being drafted No. 4 overall in 2014. That in part led to Watkins being traded to the Los Angeles Rams during training camp in 2017. However, in the nearly two years since, the Bills have yet to adequately fill the hole at the top of their wide receiver depth chart.

Jordan Matthews and Kelvin Benjamin both flopped after general manager Brandon Beane traded for them in 2017. Zay Jones, despite his improvement last season, still must ascend to justify former GM Doug Whaley and coach Sean McDermott's decision to trade up for him during the second round of the 2017 draft. Robert Foster, an undrafted rookie last season, flashed potential but is still largely an unknown quantity at the NFL level.

There was some thought the Bills would target a receiver early in the 2019 draft, but they didn't select one.

"We had guys in place on the board that we thought would've really added some different elements," Beane said last month. "It just didn't work out to take a receiver."

So, the Bills entered this offseason with No. 1 wide receiver among their top needs and could enter training camp without one, depending on how the role is defined.

If a No. 1 receiver is considered a player whose complete package of physical traits and ability make him a cut above his peers in the NFL -- like a healthy Watkins was at his peak -- then Buffalo does not have one. If a No. 1 wideout is simply the most productive pass-catcher on the depth chart, there are contenders but no clear-cut favorite at this point.

To add to Buffalo's existing top receivers -- Jones and Foster -- Beane signed free agents John Brown and Cole Beasley this offseason. Brown is a burner who has averaged the fourth-most air yards per target (14.9) since entering the NFL in 2014, but ranks 66th in catches. Beasley, formerly the Dallas Cowboys' slot receiver, is at the opposite end of the spectrum in air yards but had the most receptions (65) last season of any receiver currently on the Bills' roster.

Neither Brown nor Beasley fit the prototype of a No. 1 wide receiver, but one could emerge as second-year quarterback Josh Allen's favorite target this season. Jones and Foster are also in that mix.

"We are confident in what we have already in-house," McDermott said this month. "Adding John [Brown] to the equation this offseason with the free agency and then Cole [Beasley] as well, and then the guys that we have with Zay [Jones] and Robert [Foster] ... We are confident in those guys."

In any case, questions remain about how the statistical production of Buffalo's top wideout will compare to those across the NFL and whether it will be enough to power a winning offense.

There has been a correlation between playoff teams and teams with a wide receiver who finished the regular season ranked among the top 32 in receiving yards at his position -- a simplistic threshold but an attainable target for where a team's top receiver should finish. On average over the past five seasons, a wide receiver with 826 receiving yards has fallen within the 32 best at his position.

Since 2014, 48 of 60 playoff teams (80 percent) have featured a top-32 wide receiver. Of the 12 playoff teams without one, only four have advanced past the divisional round: the 2017 Jaguars (lost in the AFC Championship Game), the 2015 Patriots (lost in the AFC Championship Game), the 2015 Panthers (lost in the Super Bowl) and the 2014 Seahawks (lost in the Super Bowl).

Having at least one highly productive wide receiver -- even if he does not fit the traditional mold of a No. 1 receiver -- has been an attribute of most successful teams in recent seasons, and especially of teams that have advanced deep in the playoffs.

If the Bills want to become serious contenders, they might need to sort out uncertainty at the top of their wide receiver depth chart and shake off years of sub-optimal production at the position.

The most recent Buffalo wide receiver to finish within the top 10 at his position in receiving was Lee Evans, whose 1,292 yards ranked sixth in 2006. Over the past five seasons, Bills wideouts have totaled the fewest yards (10,172) in the NFL, the fewest yards after the catch (3.48) and the second-lowest receptions per target rate (55.9 percent).

Last season, Bills wide receivers had the fourth-fewest yards (1,989) and lowest yards after the catch (3.52). Starts by quarterbacks Nathan Peterman and Derek Anderson are partly to blame for those results, but even with Allen under center, Bills receivers ranked 28th in yards after catch (3.69) and last in receptions per target (50.5 percent).

Allen will play a role in determining the success of his top receiver. His receivers dropped 4.1 percent of targets last season, 10th-most for any NFL quarterback, but the difficulty of Allen's throws also played a role in the lack of production and efficiency at the position. He averaged a league-high 14.8 air yards per pass and led the league in percentage of off-target throws excluding throwaways (23.7 percent), according to ESPN Stats & Information.

A challenge for Allen this season will be choosing between using his strong arm, as well as the speed of Brown and Foster, to take shots down the field or settling for more high-probability throws underneath to Beasley and Jones. Playcalls by offensive coordinator Brian Daboll and Allen's decisions on a play-by-play basis could ultimately determine which receiver leads the pack statistically.