Two years into his NFL career and Aaron Donald of the Los Angeles Rams is widely considered the game's best defensive tackle.

With college football's Senior Bowl set to be played Saturday afternoon, it's worth remembering how Donald arrived in Mobile, Ala., two years ago and quickly enhanced his already glossy reputation as the nation's consensus top defensive lineman with an outstanding week.

Despite a sweep of every major honor (Nagurski Trophy, Lombardi Award, Outland Trophy and the Bednarik Award) following a stellar final year at the University of Pittsburgh, Donald showed up at the Senior Bowl facing questions about his ability to succeed at the next level.

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The issue, quite simply, was size. At 6-foot-1 and 288 pounds, Donald was on the smallish size for a prototypical NFL interior lineman. He needed only one workout to put any doubts to rest with a stirring performance in one-on-one drills against Baylor's mammoth Cyril Richardson, a 6-5, 340-pounder.

"Obviously he put on a great first impression," former Pittsburgh defensive coordinator Matt House told FOX Sports on Friday in a phone interview. "For all of us at Pittsburgh, it didn't come as a surprise. That's how he came to work every day."

Donald, who led all NFL interior linemen with 69 sacks to go along with 11 sacks this season, lit up the Internet following his practice performances against both Richardson and Notre Dame's ZacK Martin, a first-team All-Pro selection as a rookie with the Dallas Cowboys.

"You knew he was very talented and highly competitive," said House, now the defensive coordinator at Florida International University, of Donald. "He plays with such great leverage and quickness."

Donald drew rave reviews nationally before the Senior Bowl was even played. NFL.com and USA Today each praised Donald's "dominant" first-day showing. CBS Sports called him an "unstoppable force" and Packers.com termed him "unblockable" while citing his "devasting" first step.

Donald had received a "borderline first-round grade" from ESPN's draft guru Todd McShay entering Senior Bowl week, but he wound up as the No. 13 overall pick of the Rams. Donald made a seamless transition to the pro game, earning NFL Defensive Rookie of the Year honors in 2014 and a first-team All-Pro selection this season.

"There were some question marks on him," House acknowledged. "The thing about Aaron, whether in practice or in games, is he likes to compete. He truly embraces competion. ... I'm not surprised at all by his success."