As anyone familiar with the mechanics of throwing knows, the legs provide the base and power to deliver a ball with velocity.
While the Eagles have stopped short of declaring Carson Wentz ahead of schedule in his recovery from knee surgery – despite his surprising involvement in spring practices – the best indicator that the quarterback is on track to meet his goal of being ready for the season opener might come from his right arm.
Wentz's throws seemingly are moving at a clip as fast – and possibly faster — than they were before he was hurt. There could be myriad reasons. Throwing a football is as complex as mechanics get in sports, but if Wentz's surgically repaired left knee wasn't close to being healed, his passes wouldn't be traveling at near the speed they have been over the last few weeks.
"The ball has the same zip, if not more," Eagles tight end Zach Ertz said Wednesday. "It's definitely coming."
Ertz has caught passes from Wentz the entire offseason, but only this week have they come during 7-on-7 drills. With each practice that has been open to reporters in the last three weeks, the Eagles have increased Wentz's workload.
"Part of the rehab process with him is giving him a little more — I don't want to say freedom — but a little more practice time," coach Doug Pederson said. "And one of the controlled environments that we can, obviously, put him in is a seven-on-seven situation."
There is no play at the line of scrimmage during seven-on-sevens, so Wentz doesn't need to worry about evading the rush or a lineman accidentally contacting him. Quarterbacks wear red jerseys, marking them off limits, but full 11-on-11 drills are as close as teams can get to simulating a game, even when the players are only in shells and shorts.
>> READ MORE: Eagles practice observations
Wentz still has many steps to take before he's completely cleared. The throwing component is an important one, but he must show that his knee is capable of withstanding full acceleration, cutting, and planting. With the six-month anniversary of his injury Sunday, and the Eagles' season opener three months away, that answer is still unknown.
Pederson declined to say whether Wentz was ahead of schedule.
"I'm not a doctor," he said. "I can't really answer that."
He said that he was encouraged by the progress all the injured Eagles have made, and cited tackle Jason Peters, running back Darren Sproles, and linebacker Jordan Hicks. The Eagles weren't "pushing any one of these players to get back," he added.
But there is concern that Wentz will rush his return. The Eagles can pull the reins back – Pederson has downplayed his quarterback's progress for months – but many teammates have mentioned Wentz's competitiveness when asked about his increasing participation in workouts.
More than any trait, however, they cite his work ethic.
"The dude's a hard worker," center Jason Kelce said. "He comes in here every single day, and he's been like that the moment he stepped in this building. To say that I would be surprised by him being ahead of schedule, I don't think is accurate."
Wentz spoke at the beginning of organized team activities two weeks ago, but he has been unavailable for interviews since. But his performance, at least during three open practices, has spoken volumes.
His involvement in seven-on-sevens amounted to just two sets of two plays with the second-team offense – Nick Foles continued to work with the first unit — but Wentz completed all four passes. The first two landed in the familiar hands of Ertz, on a short sideline route and a crosser underneath.
"Just like old times," Ertz said. "Just like riding a bike."
On the next set, Wentz strung a rope to rookie tight end Dallas Goedert over the middle and connected with wide receiver Mike Wallace on a slant. The faces at the end of those passes were new, but Wentz's guise wasn't.
"When he lines up and he's out there, he's trying to shred the defense," receiver Nelson Agholor said.
Wentz partook in the early portion of individual drills, but when the squad split for special-teams work and the quarterbacks threw separately, he walked to another field, took a knee and restrapped his brace. He eventually jogged back to the quarterbacks and jumped in for a throw.
When the last set of team drills began, Wentz took off his brace and ran a series of sprints on a separate field. He returned and watched until the end but was an active presence.
"Even if he's not the one who threw me the ball," Agholor said, "if I'm in there with Nick, I'll still ask Carson, 'Hey, what could I have done? What did you see?' "
In other words, not much has changed. Wentz will still move carefully on occasion. And he hasn't thrown as much – perhaps one reason for the apparent increase in velocity – but there are few discernible signs of injury.