Maclin insisted throughout the spring that he is healthy and that the knee is not in the back of his mind.
"You can't think like that, because the minute you go out there timid, that's when something bad happens," Maclin said. "I go out there and push myself. I feel good, I don't feel I lost a step, and I'm getting in and out of breaks well."
If the Eagles offense wants to come close to its record-setting 2013 pace, Maclin must return to form. The team showed its confidence in Maclin's recovery when it re-signed him before free agency opened and then released DeSean Jackson one month later. He is the No. 1 receiver, the most experienced and the most productive, and he's in position to help replace Jackson after a Pro Bowl campaign.
One player cannot singularly replicate Jackson's production, and the additions of Jordan Matthews, Josh Huff, and Darren Sproles will combine with returning players to help fill the void. But the biggest addition was Maclin, who might have been the receiver making the winter trip to Hawaii had he been healthy last season.
The team's brass overflowed with confidence about Maclin one year ago, believing that his skill-set was ideal for Kelly's offense and that his personality was the type they wanted in the locker room. Maclin was similarly confident, as evidenced by his decision to sign a one-year deal in February and eschew a long-term deal from the Eagles.
"You just have to have faith in the whole process and with everything that's come along with it, which I have," Maclin said. "It's been going good."
Maclin missed five games in four seasons before last year. He also tore his right ACL when he was a freshman in college, but Maclin pointed out that technology and medicine have improved since then. And though he has yet to record a 1,000-yard season, the former first-round pick had more receiving yards through his first four seasons than any other player in Eagles history.
He also has an established connection with quarterback Nick Foles. When Foles started six games in 2012, Maclin had two 100-yard receiving games and caught 36 passes for 472 yards and three touchdowns. That accounted for 22 percent of Foles' completions, 28 percent of his yards, and 50 percent of his touchdowns.
"Having that history that we have, and the OTAs last year, throughout the spring and the summer, we've had a lot of work in," Maclin said.
Foles said that he and Maclin understand each other on the field, and that "several times" this spring Maclin adjusted a route to create a connection.
"That sort of tells you we're on the same page," Foles said.
His value to the Eagles is clear. Maclin is thickly built, carrying nearly 200 pounds on his 6-foot frame. He can play multiple spots, able to go inside or outside. He also has run-after-the-catch ability - 35 percent of his career receiving yards have come after the catch, according to Pro Football Focus. And Maclin is capable against man-to-man coverage, a requirement in Kelly's offense. But Maclin has not yet lived up to his first-round billing and become a top receiver in the NFL.
Maclin remained in Philadelphia during his rehabilitation last season and attended meetings. That helped him stay connected with the team and understand the system. So, when he returned this spring, the only question was his body - not his mind.
"I really don't see anything different from when he was feeling good," wide receivers coach Bob Bicknell said. "He's done everything we asked him to do, from the standpoint of being here every day."
Bicknell added that Maclin still needed to get in football shape. But the knee is not a concern to the coaching staff or the player, even if a practice falls silent at the sight of Maclin on the ground.
By Maclin's own admission, the next big test will come when he's tackled. The question won't just be whether he can stand up after a hit. It will be whether he can return to his pre-injury form and thrive as the Eagles' top receiver.
"Gut feeling," Foles said, "I think he's better."