"That will help you a lot," Harbor said, "knowing you got 50 more catches after practice than your competition."
All the work will be critical for Harbor, who had only 22 catches for 235 yards and two touchdowns in his first two seasons. Of course, he's been a backup tight end on a team with offensive firepower.
For at least the next few days, though, Harbor will have the chance to play as the first-team tight end. Starter Brent Celek missed practice Friday while recovering from a slight medial collateral ligament sprain in his right knee. Celek will be day-to-day while recovering.
"Mild knee sprain, doesn't hurt that bad," Celek said. "Just something that I have to be cautious about."
The Eagles worked out veteran Visanthe Shiancoe earlier in the week before he signed with New England, and coach Andy Reid and general manager Howie Roseman planned to discuss whether to bring in an additional tight end. Veteran Jeremy Shockey is likely not in consideration.
"Not right now, no," Reid said.
Considering Celek could soon return, it sounded as if the Eagles would not sign a tight end simply to balance the reps in camp. The Eagles used undrafted fullback Emil Igwenagu as a tight end during Friday's practice.
"We just got to weigh that out, whether we bring somebody else in or do this," Reid said. "When you bring somebody else in, and if they haven't been in a camp, then they got to take a three-day buildup, so it's not going to help you tomorrow. We got to look at those things. And Brent could be back the next couple days. It could be a week."
Reid wants Celek on the field, but if there's any solace to be derived from the minor injury, it's that the other tight ends on the roster will have more opportunities to develop in Celek's absence. The spotlight then shines on Harbor, who was an intriguing prospect as a 2010 fourth-round draft pick but has yet to make a significant imprint.
In fact, the reason the Eagles considered other tight ends was to push Harbor. Harbor accepted that as a challenge rather than a slight, and Celek stood up for his position mate on Friday when he implied that Harbor has not yet revealed all that he can do.
"Clay's a great player," Celek said. "He didn't have a minicamp last year, and training camp was different last year. But Clay's got a lot of talent."
The talent excited the Eagles when they drafted Harbor, who was a three-time Division I-AA all-American at Missouri State and set the school record with 150 career catches. A sports hernia limited Harbor in 2010, and the lack of a 2011 offseason stunted the development that a player often gains between his first and second seasons. Now in his third training camp and with the benefit of a full offseason, Harbor must demonstrate that he can reach his potential in Philadelphia.
"I've always felt I was a pretty good athlete; I like to hit, so I'm physical in that aspect," Harbor said. "It's the confidence in knowing everything I got. . . . I feel like right now I'm 100 percent on every play that they call. It's just second nature now."
Whether that translates onto the field will not be determined just by how well Harbor plays, but also if the ball can come his way in an offense that already features LeSean McCoy, DeSean Jackson, Jeremy Maclin, Jason Avant, and Celek. Harbor caught passes during Friday's team drills - an encouraging sign, considering he struggled with his hands during spring drills - but he did it in Celek's absence.
Harbor said the best way to earn receptions is to become trustworthy. He admitted that the coaches have seen "flashes" from him but not consistency. Until Celek returns, Harbor can develop trust. Once Celek returns, Harbor can maximize that trust.
"With trust comes opportunities," Harbor said. "It'll be a good time out here to get that done and show them what I can do consistently."
Contact Zach Berman at firstname.lastname@example.org or follow on Twitter @ZBerm.