It's not route running or reading defenses where Fells thinks Hockenson can get better...
In fact, it has nothing to do with how Hockenson played in his two seasons with the Lions. Hockenson made the Pro Bowl last season, and the way he performed in minicamp showed he is putting in the work to move up the pecking order of the NFL's top tight ends.
It's the touchdown celebration where Fells thinks Hockenson has come up short. With two TD catches as a rookie and six last season, Hockenson has had enough chances to display his celebration routine.
"We haven't discussed it too much," Fells said with a smile. "His whole big thing is he catches it, falls down and pops up and throws the arm up.
"Anything is better than that. We talked about what his dance moves are, I haven't taken him to a club or anything due to COVID to see if he has those kind of moves.
"Right now, we're just trying to find what looks good on him."
Seriously, dance moves and celebrations aside, the Lions look like different to Fells than the team he played for in 2017, his one season as a Lion.
After three previous seasons with the Seahawks, Fells had 17 catches for 177 yards and three TDs with the Lions in 2017. He moved on to Cleveland for one season the next year and spent the last two years with Houston.
Fells was used more as a receiver in Houston than in any of his other stops. He had 34 catches and seven TDs in 2019 and 21 catches and four TDs in 2020.
Fells was struck by how much the Lions have changed in the last three years.
"The only similar thing is the building and the city," he said. "It definitely felt like a brand new team. It's fun being back in the city and seeing the building."
Fells and Hockenson have talked about how they'll be used in situations with multiple tight end formations.
"i've always thought of T.J. being an extremely athletic and talented player," Fells said. "Being able to come in here and mentor him a little bit is an awesome thing.
"I can go in there and do a little more of the dirty work. I had a conversation with him already. When we're both in there, i can line up and give him more time to get open.
"He can punch that touchdown total up to 12, and I can help him with his celebration."