The New England Patriots' one-two punch in the passing game is indisputably Rob Gronkowski and Julian Edelman. For the Cincinnati Bengals, few would argue that A.J. Green and Tyler Eifert are opposing defenses' main concerns, and when Kelvin Benjamin returns from injury for the Carolina Panthers, Benjamin and Greg Olsen should join that group.

So what about Sammy Watkins and Charles Clay?

On paper, the Buffalo Bills' top receiver-tight end duo should be in the conversation with other top tandems around the league -- but it's not. With Watkins sidelined likely until the start of the regular season because of a broken foot, the spotlight is on Clay to fill the void in practice and be ready to carry the load if Watkins has to sit at any point again this season.

Not only did the Bills make a huge investment in Watkins by trading two first-round picks to move up five spots in the 2014 draft to select him, but they also opened their wallets to pry Clay, a transition-tagged free agent, away from the Miami Dolphins a year ago. The Bills doubled down on Clay this spring when they restructured his five-year deal to push $7.5 million of his $24.5 million in guaranteed money into future years, increasing his salary-cap hits to a hard-to-dodge $9 million from 2017 through 2019.

Clay owns the fourth-largest cap hits on the Bills in 2017 and 2018, and his contract is currently the seventh-richest among NFL tight ends, averaging $7.6 million per season. That means Clay's usage and production should be close to that of the top tier of tight ends in the NFL. But is it?

To find out, I chose five of the NFL's best tight ends last season -- Gronkowski, Eifert, Olsen, Kansas City's Travis Kelce and Tennessee's Delanie Walker -- to compare both their usage in their respective offenses and their production to Clay's. I eliminated games in which those players saw limited action because of injury and, from among those "healthy" games, I calculated how often each player ran a pass route, what percentage of receptions and touchdowns resulted from those pass routes and how many receiving yards each player averaged per pass route:

Clay ran pass routes in 77.7 percent of dropbacks by Bills quarterbacks, indicating that he was used as a receiver in the passing game about three times as often as he was being used as a blocker. That was a notch below Olsen, Gronkowski and Walker, but Clay was certainly given opportunities by offensive coordinator Greg Roman to make plays in the passing game.

It's also clear that Clay got open and that either Tyrod Taylor or EJ Manuel threw the ball to him. He caught passes on 15.4 percent of his pass routes, more often than Gronkowski and Eifert. But it was Clay's ability to stretch the field and score touchdowns where he lagged behind his peers. He averaged 1.60 receiving yards per route run, the lowest among all six tight ends, and his 0.9-percent touchdown rate was also the lowest.

If the Bills want the one-two combination of Watkins and Clay to live up to the investment they made in both players, Clay must make a greater impact as a big-play and red-zone tight end.

Clay must avoid injury, too. He missed practice time late last August because of lingering knee issues that might have shied away the Dolphins from making more of an effort to re-sign him. He showed up on the injury report last October with a calf injury and again in December with a knee injury. He then suffered a back injury in a Week 14 loss to Philadelphia that kept him out of the final three games of the season.

Meanwhile, Watkins has dealt with at least seven injuries in his first two years in the NFL, causing him to miss only three regular-season contests, but more often limiting him in practice and in games.

With Watkins recovering from a broken foot this summer, the Bills will run through training camp and the preseason with fourth-year player Robert Woods as their top receiver. General manager Doug Whaley and his top lieutenant, player personnel director Jim Monos, both spoke in January about the team's desire to upgrade from Woods. That didn't happen, although the Bills will have a stable of veterans -- Leonard Hankerson, Marquise Goodwin, Greg Salas, Greg Little and Jarrett Boykin -- as well as sixth-round rookie Kolby Listenbee vying for reps across from Woods during camp. The team is also hosting veteran receiver Andre Roberts, cut by the Washington Redskins this week, on a free-agent visit Friday.

But the discussion about who picks up the slack for Watkins -- not only during his absence this July and August at training camp, but also whenever his next injury hits -- should start not with Woods nor any other receiver on the Bills' roster, but with Clay.