Maclin went down at the end of a non-contact drill and appeared to be in pain while he was on the ground for several minutes. He was helped onto the cart and needed assistance getting off it and going into the team's practice facility.
"I was devastated," Maclin said Sunday. "It wasn't the fact that it hurt, it was the fact that I knew what happened so I was emotional, knowing what was at stake. This is something that I love to do. I love to play football and knowing I'm not going to be able to do that, knowing that I'm not going to be a part of this new era here in Philly this year."
Maclin said Sunday he will have surgery to repair his torn right ACL next Tuesday. Dr. James Andrews will perform the operation in Alabama.
On Saturday, Maclin thanked fans for their support on Twitter.
Appreciate all the love and support twitter fam....sad day but I have setbacks my entire life. Minor setback ... http://t.co/DiFGrrmI5D
— Jeremy Maclin (@jmac_18) July 27, 2013
The oft-injured Maclin, entering the final season of his five-year rookie contract, has played an entire season just once in his career.
Several players tweeted messages of support to Maclin, including Eagles quarterback Michael Vick.
We doing this for you @jmac_18 all prayers going out to you. We know your coming back even stronger in 2014. Luv you bro!!
— Mike Vick (@MikeVick) July 28, 2013
We may be on rival teams @jmac_18 but we are still human and I sent prayers up for you brother along with all others injured today
— Robert Griffin III (@RGIII) July 27, 2013
General manager Howie Roseman on Sunday praised Maclin's character and decision not to holdout for a new contract.
"Jeremy's a heck of a player, great character, hard worker, he had a great offseason and it's disappointing for him and it's disappointing for us," Roseman said. "He's 25 years old. He'll come back from this. He's overcome a lot of adversity in his life, he's got tremendous character. We're hurting for him but at the same time, we have to keep going and find guys."
Riley Cooper took reps with the first team opposite starter DeSean Jackson in Sunday's practice at the Linc. Veteran Jason Avant, Damaris Johnson and rookies Russell Shepard and Ifeanyi Momah also have a chance to compete for the starting spot.
After catching a career-high 10 touchdown passes in 2010, Maclin has combined for just 12 scores over his past two campaigns. He had an Eagles-leading 69 receptions for 857 yards and seven TDs last season. He has averaged 64 catches, 863 yards and six TDs in his first four seasons. His best year was in 2011 when he had 70 receptions for 964 yards and 10 TDs.
The Eagles on Saturday signed wide receiver David Ball to the 90-man roster. The 29-year-old Ball played for Eagles coach Chip Kelly at New Hampshire, and broke Jerry Rice's Division I-AA record for touchdown receptions. Ball spent time in training camp with Chicago and the New York Jets in 2007-08.
Information from The Associated Press was used in this report.