The Steelers tried to replace Harrison once before, in 2013, but Jarvis Jones didn't work out and Harrison returned to the team and, at age 39, will begin his 15th season, this one with the younger brother of Houston Texans superstar J.J. Watt as his backup.
T.J. Watt, like his brother, is a converted tight end who developed quickly as a pass-rusher.
Watt, 6-4 1/2, 252, had 11.5 sacks last season, his first as a full-time starter. He also had 15.5 tackles for loss, an interception, two forced fumbles and a fumble recovery.
He's a long-armed, fluid linebacker who played the same position in Wisconsin's 3-4 scheme.
A high school quarterback in the state of Wisconsin, Watt went there as a tight end, redshirted in 2013, and sat out the 2014 season with a right patella subluxation, and had the same injury to his left knee in the spring of 2015. He was moved to defense in the fall of 2015 and played in eight games as a backup before coming on as the starter last season.
Watt posted sensational times and distances at the NFL Combine. He ran a 4.69 40, had a vertical jump of 37 inches and a broad jump of 10-8. But his most impressive times came in the agility drills. He had a position-best 3-cone time of 6.79, and his short shuttle time of 4.13 tops the times of all three of the Steelers' starting cornerbacks at their respective Combines.
Watt's one knock is a lack of strength. He benched only 21 times and will likely struggle against the run as a defensive end in the Steelers' nickel. But his passion for the game and work ethic should help him improve his strength and technique at this relatively new position.
"T.J. Watt is somebody we've had our eye on since the early fall," said Steelers GM Kevin Colbert. "I looked at him and said, 'Coach, this kid's a first-round pick.'"
The Steelers spent an evening with Watt before the Wisconsin pro day.
"He's really only scratching the surface as a defensive player," Colbert said. "We don't even think he's a complete product at this point. We're excited."
"We saw some things that are exciting to us, his hand usage in particular," said Coach Mike Tomlin. "He's worthy of the pick, but boy we're excited about the upside and growth considering the short time he's played the position."