Heuerman -- a third-round pick in this year's draft -- hurt his knee back in May, but is making good progress on his way back from the injury.
"I wouldn't call them big strides," he said with a laugh on Thursday, "not literally, because they're actually pretty small strides—but I'm making progress."
Heuerman will likely miss the entirety of this upcoming season, but that hasn't put a damper in his recovery.
"Each day’s a bigger step, which it kind of sounds corny and it kind of sounds like I’m just saying that, but it really is," Heuerman said.
Davis signed with the Patriots last month, but previously spent his first seven seasons with the Redskins.
Davis missed all of the 2014 season due to a suspension for violating the league's substance abuse policy.
He broke out in 2013 as an undrafted free agent with seven touchdowns, but then the Lions drafted another tight end in the first round the following season. Fauria now expects to hit his stride and improve on last season's six catch, 74 yard totals.
“Extremely frustrating,” Fauria said, per the team website. “But it’s something you have to overcome. Football is frustrating, you know. Everyone has injuries. Everyone has trials and tribulations and it’s how you answer them and how you come back. I’m expecting myself to come back strong.”
Fauria is a huge target a 6-foot-7 and the Lions hope they can use that to their advantage next season.
“He has a unique skill set,” head coach Jim Caldwell said of his big tight end. “When you’re not able to utilize everything that’s available to you, you know, obviously you have to find other ways to do it.
“So, he brings to the table a little something that you can’t teach. He has height and he can position himself, particularly in the red zone, extremely well.”
Mulligan, 30, has a total of 16 receptions for 160 yards and two touchdowns in his seven-year career.
Harbaugh doesn't believe the injury to be serious. Williams was selected by the Ravens in the second round of the draft out of Minnesota. In his final collegiate season, Williams caught 36 passes for 569 yards and eight touchdowns.
Donnell was using the walking boot to heal from Achilles tendinitis in his left heal.
Sudfeld suffered a knee injury during practice last week. In 16 games last season, Sudfeld caught five passes for 85 yards.