Heuerman, a third-round draft pick last weekend, became the second rookie league-wide to suffer a season-ending ACL tear during a non-contact practice. Jacksonville Jaguars defensive end Dante Fowler Jr. suffered a torn ACL on Friday and is expected to miss the 2015 season.
The Broncos were in jerseys and shorts -- no helmets -- for an afternoon workout. Heuerman was in the open field during a special-teams drill, planted his left leg to cut and the knee buckled. He was taken for a MRI early Saturday evening, and it confirmed the initial diagnosis by the team's training staff that he had torn the ACL.
He will have surgery after the swelling in the knee has subsided.
"I feel terrible for Jeff and this is an unfortunate situation," Broncos coach Gary Kubiak said. "Jeff was going to be a big part of our team this year, and he's still going to be a big part of our team and organization in the future. He'll get well and be with us as part of this team throughout his rehabilitation."
Heuerman, a captain on Ohio State's national championship team, was injured in the last of four practices the Broncos held for its rookies this weekend.
The injury will impact the team's rotation at the position. Though the rookies had taken part in just two days' worth of practices, the Broncos were already expecting Heuerman to play a great deal in 2015.
Said Kubiak on Friday: "He's a good looking player and I like his work habits. He's very smart. He's played in a big program, so nothing is [too] big of a stage for him. Walking around this locker room, being around people, watching him prepare for practice, you can tell. He's got a bright future. The quicker we can get him going, the more he helps us with [Owen Daniels] and with our group that we have with Virgil (Green] and [others]. We're expecting a lot out of him."
After Friday's practice he too had expressed optimism about what the season would bring.
"It was nice to finally run around and play some football,'' Heuerman said. "It was a long pre-draft process, so it's nice to finally get out there on the field and play some actual football ... I'm here to compete. I'm here to learn. I know those guys have been around for a while. They've played a lot of professional football. I'm here to learn from them and do what I can to help the team win. At the end of the day, that's what matters to me.''
Heuerman had left foot surgery in the spring of 2014 and missed one game early in Ohio State's season as he finished his recovery. He injured his right ankle in the Buckeyes' Sugar Bowl win over Alabama and revealed after the draft that he took painkilling injections in order to play in the national championship game against Oregon.
He had 17 catches and two touchdowns for the Buckeyes last season to go with 26 receptions and four touchdowns as a junior.