He made jaw-dropping catches throughout training camp, earned a role in the offense as a true freshman and turned in one of the most memorable highlights of the 2011 season when he straddle-leaped a Washington State cornerback in the Apple Cup.
And yet there was one thing Williams had yet to prove -- until last Thursday night.
In front of a national television audience, and while playing against a nationally-renowned defense, the former Skyline High School star showed once and for all that he's capable of being a consistent, go-to receiver at UW.
Williams's 10 catches for 129 yards, both career highs, gave him the kind of game for which the Huskies had been waiting since veterans like Jermaine Kearse and Devin Aguilar moved on -- thus leaving Williams in the de facto role of this season's go-to guy.
"I just feel like my abilities are a lot higher than last year," Williams said after a Wednesday morning practice. "Last year, I was stepping in, and I just wanted to make a name for myself. Now, I want to build on that name. I have goals for myself."
Williams caught 36 passes for 427 yards as a true freshman, making a few eye-opening catches along the way but mostly ceding the important catches to guys like Kearse, Aguilar and tight end Austin Seferian-Jenkins.
Coming into this season, Williams wanted to make a bigger impact -- at UW, on the West Coast and on a national level. He wanted to be the Huskies' main receiver, to win a Pacific-12 Conference title, to be named first-team all-Pac-12 and to win the Biletnikoff Award, which goes to the nation's top receiver.
Those were pretty lofty goals heading into the 2012 season, and no one seemed to be engraving any trophies after he caught a modest 15 passes through the first three games.
But after last Thursday's win over eighth-ranked Stanford, Williams is looking more and more like the go-to receiver the Huskies need him to be.
"I always try to be that guy that we're going to go to every game -- me and Austin," Williams said. "We just do what we're supposed to do. The coaches like it when the ball's in our hands -- that's their goal, and my goal is to just get better."
Of course, the Stanford game had its share of Williams-like highlights as well. He made an improbable, diving sideline catch between two Stanford defenders to keep a scoring drive alive late in the first quarter, then added the game-winning touchdown on a quick-throw-and-spin-move that went for 35 yards with five minutes left in a 17-13 win.
"My favorite would probably be the game-winning touchdown," Williams said Wednesday. "That was pretty cool. But the other catch was pretty cool, too. I just have to make more of those plays. Those are plays that I'm expected to make -- and I expect that from myself."
Head coach Steve Sarkisian said Williams' emergence has had a lot to do with what happens between Saturdays. After Williams went through what his coach called an "awesome" practice Wednesday, Sarkisian said that those types of mid-week performances are becoming more and more common for the sophomore receiver.
"He's been practicing so well," Sarkisian said. "And when you do that, it carries right over to the games. That's why you play well in football games, because you practice well. Kasen has really adopted that mentality: every snap in practice is a championship snap. And the result is that he's playing well on game day."
The Huskies have made it no secret that they intend to get Williams the ball early and often. He was a target on UW's first or second snap in each of the Huskies' first three games, and one of the staples of the revamped offense has been a quick throw to Williams in the flat.
"I know I can count on that guy," quarterback Keith Price said. "He's going to bring it every day, and he's very reliable."
With an NFL frame (6-foot-2, 216 pounds) and a unique ability to both shake off press coverage and run through tackles, Williams is the kind of receiver who could soon draw double-teams and attention from opposing safeties. He said that hasn't really happened to date, but things might change after the Stanford win.
"I hadn't really done anything prior to that game to make any defense key on me," he said. "This week might be a little different, but I haven't really done anything except for this past week, so we'll see what happens."
Having already shown the potential to thrive in the role of No. 1 receiver, Williams might soon start getting treated like a No. 1 receiver by opposing defenses.
And then, the high-profile receiver with the lofty goals will have something to prove again.
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