Robinson was the 199th overall selection and will start his NFL career with the Washington Redskins, after he was the 'Skins' fourth-round pick.
"He's a leader," said Texas coach Mack Brown. "He's big. He's strong. He's fast. He can play all over the field and he was also one of our best special teams players.
"Keenan came in tall and thin and left about 240 pounds," Brown said. "So he has improved his strength, his flexibility and therefore his range in his ability to make the big hit more than any player that I can remember."
Robinson started 39 games during his Longhorn career, and was a two-time Butkus Award semi-finalist. He had 317 career tackles (172 solo), 5.5 sacks, 25 tackles for loss, 14 pressures, two interceptions, two fumble recoveries, three forced fumbles and 15 passes broken up.
That included a strong 2011 that saw Robinson make 106 tackles, including 10 tackles for loss. He earned Holiday Bowl Defensive MVP honors after making 10 tackles, including two tackles for loss, in the Longhorns' season-ending win.