WEST LAFAYETTE, IND. — Ralph Sampson III looks for Rodney Williams prior to tipoff every game. And when Sampson finds him, the 6-11 Gophers center rattles off his list of demands.

"Right before every game, I tell him, 'Give me at least three dunks and at least one of them has to be nasty and on somebody,' " Sampson said. "He always delivers."

Teammates, fans and TV execs love Williams' acrobatic dunks, which often crack the top-10 plays on "SportsCenter" and blow the roof off Williams Arena. Few players in America -- at any level -- possess the leaping ability and athleticism of the 6-7 sophomore from Cooper High School.

With Devoe Joseph gone and Al Nolen injured, however, the bar has been raised. Williams -- averaging 7.1 points, 3.4 rebounds and 2.4 assists and 1.0 blocks in Big Ten play for the No. 16 Gophers -- is expected to consistently contribute on offense and defense.

"I definitely have to [be more aggressive] especially now with Al out," said Williams, whose team visits No. 12 Purdue on Saturday. "If my shot's not falling on offense, then I've got to be tough on [defense]."

In coach Tubby Smith's new tri-tower lineup -- Trevor Mbakwe, Colton Iverson and Sampson likely will all start again Saturday, Smith said -- Williams plays shooting guard. He is expected to guard smaller players and hit shots from outside.

Williams swished shots from all over the floor after Friday's practice. Improved shooting is critical because he's only 4-for-29 (13.8 percent) from the three-point line this season. He had missed 17 consecutive threes before making two in the second half of a 69-64 victory at Michigan last week.

But when Williams attacks the basket, his athleticism and dunking ability are too much for most defenders, who can only watch as he climbs. If he can fly like that, why doesn't he go to rim more often?

"I like to get the ball inside and see what everybody else is going to do before I start being aggressive, because sometimes when I start out being real aggressive, I get to being overaggressive," Williams said.

Smith said he wants Williams to assert himself on offense, where he is often matched against a smaller defender, especially playing shooting guard. Against the Boilermakers, 6-4 E'Twaun Moore or 6-3 Ryne Smith probably will guard him.

Smith also wants Williams to play with more control.

"I like him to just go to the basket," Smith said. "I hate when he double-pumps, because I figure nobody's going to be up there with him. Lots of times, he's his own worst enemy."

Williams has shown improvement on the defensive end of the floor. In a 67-64 loss at undefeated Ohio State Jan. 9, Buckeyes sharpshooter Jon Diebler went 3-for-8 with Williams in his face most of the game.

When the Gophers beat then-No. 8 Purdue 70-67 Jan. 13, Williams' pressure limited Moore, who is averaging 18.0 points per game, to a 2-for-14 outing. Moore is 3-for-28 in his past two games against the Gophers.

Senior co-captain Blake Hoffarber said Williams' defense can reach the level of former Gophers forward Damian Johnson, who graduated last spring.

"[Williams] can be a great defender," Hoffarber said. "... He's got the length, the athleticism."

Even as Williams adds more nuances to his arsenal, dunking will remain a key part of the way he plays.

On Friday, teammates talked about his 360-degree dunk at Michigan last season like it just happened. Mbakwe said he wonders why defenders even bother once Williams leaves the ground.

"I don't understand why people still jump with him," Mbakwe said. "They must not be reading the scouting report."

Against Northwestern on Wednesday, Williams sailed over Drew Crawford for a thunderous slam in the first half.

"When I go out there and just play and not think about it, that's when stuff like that happens for me," Williams said. "I just gotta go out there and play my game."