The Bills signed the former Miami Dolphins tight end to a five-year, $38 million deal in 2015, but until last December, Clay's production in the passing game was limited. He ended the 2015 season with 528 receiving yards and three touchdowns, and through the first three months of the 2016 season, he had only 323 yards and no touchdowns.
"Watching him on film [this offseason], he looked like a different guy [in 2016] from when I saw him in Miami," Bills first-year offensive coordinator Rick Dennison said Monday, adding that Clay looked "dynamic" when he played in Miami.
Clay missed the first game of last December, a loss to the Oakland Raiders, to be present for the birth of his child. In the eight games since -- four to end the 2016 season and four to begin this one -- Clay has scored six touchdowns, double what he produced over his first 24 games in Buffalo.
The resurgent Clay reached a new level in Sunday's victory over the Atlanta Falcons, in which he caught five passes for 112 yards, the most yards he has gained in a game since 2014. Clay caught passes of 44 yards (second quarter) and 34 yards (third quarter), jump-starting a pair of scoring drives for Buffalo (3-1).
With 18 catches for 227 yards and two touchdowns through four games, Clay is on pace for 72 catches for 908 yards and eight touchdowns. Such a season would top Clay's career highs of 69 catches for 759 yards and six touchdowns with Miami in 2013.
So what has changed for Clay since the first three-quarters of last season?
"Me going to him more in some of the one-on-one matchups and taking advantage of those," quarterback Tyrod Taylor said Wednesday. "I tried to [do that] over the past couple of years. Probably did more of it towards the end of last season than the beginning part of it, but [I] just trust him to make those plays, and we’ve been on the same page and he’s going out there and playing at a high level."
Clay is Taylor's most targeted receiver this season, with 25, and those 227 receiving yards leads the Bills. Clay has caught passes on 16.7 percent of his routes run, more than double the rate of any of Buffalo's wide receivers -- a group that includes Jordan Matthews (8.8 percent), Andre Holmes (8.8 percent) and Zay Jones (3.4 percent).
Taylor has targeted Clay on 23.1 percent of his routes run this season, a slight uptick from 2016 (21.1 percent) and 2015 (21.3 percent). In both of those seasons, top receiver Sammy Watkins had a higher target rate. Watkins was targeted on 24 percent of his routes in 2015 and 21.8 percent in 2016.
It would seem logical to think Clay has benefited from the Bills' offseason trade of Watkins and the team's current lack of a bona fide No. 1 wide receiver. However, Taylor does not see a correlation.
"I wouldn’t say Sammy took away from [Clay's] targets," he said. "Like I said, it’s more so just me growing with Charles, us growing with each other going into Year 3 of playing with each other. Knowing what he does well and me just trusting that he’s going to go out there and make that play."
Clay missed practice Wednesday because of a death in his family but is expected to play Sunday against the Cincinnati Bengals. With Matthews set to miss the game because of a thumb injury, Clay could play an even larger role in the Bills' offense.
"I can’t say what was the difference between last year and this year, I just like what he’s doing," Dennison said. "He’s done a great job, he’s an eager worker, willing to listen, and puts his time in every day.
"He’s running fast, he’s playing fast. [Sunday in Atlanta] he was exceptional."