The worst moment of the worst loss of the Eagles' 2016 season, a 32-14 drubbing at the hands of a struggling Cincinnati Bengals team last Dec. 4, might have been when veteran safety Rodney McLeod stood, seemingly frozen, while Bengals running back Jeremy Hill strode unencumbered into the end zone from 2 yards out. It was the first touchdown of the day for Cincinnati, which would put points on the board in each of its first six possessions.

McLeod, a fifth-year player who had built his NFL career on hustle after going undrafted from Virginia, did not hustle. He was paralyzed by indecision, thinking about not just his assignment but the assignments of the players around him, who had  proved they couldn't always be relied upon as the Eagles defense plummeted from top-five status through the season's first nine games to 13th overall, 20th in yards per play, by season's end.

For most of the season, McLeod was one of the Eagles' best defensive players — steady, smart, physical. But when the pass rush slowed and the corners crumbled, McLeod, too, sagged.  That's what happens when one part of a defense struggles; eventually, the entire group struggles.

Which is a roundabout way of saying that as training camp gets underway Monday for rookies, quarterbacks, and select veterans, the Eagles' apparent inability to improve their secondary during the offseason stands out as the team's most glaring weakness, potentially the biggest factor standing between them and the playoffs.

"You don't want to be the weak link," McLeod said last month, as minicamp ended. "[Coordinator] Jim Schwartz always stresses there is no weak link on this defense. That's what we stress in our room, specifically the secondary."

Schwartz said, "We understand where we were last year and how it affected our defense, and we need to be better at our corner position, for sure."

They are hoping that additions to the pass rush – Tim Jernigan, Derek Barnett, Chris Long — will take some pressure off the back end, that McLeod and the other starting safety, defensive leader Malcolm Jenkins, can make up for a young and unheralded gaggle of corners. And they're hoping, with little safety depth, that McLeod (27) and Jenkins (30 this December) again will be healthy enough to start all 16 games.

"We have a long way to  go, obviously,'' defensive backs coach Cory Undlin said last month. And that was before Pro Football Focus deemed the Eagles secondary the worst in the NFL. (PFF deems the Eagles' offensive line the NFL's best – a ranking that seems equally hyperbolic.)

Both Eagles starting corner jobs and the nickel spot are in play as camp begins, which is unusual, and alarming.

"Whoever's the best two guys for those spots are going to  start," noted Patrick Robinson, the most heralded veteran corner addition of the offseason.

Robinson, a 2010 Saints first-round pick, has had his moments in seven NFL seasons, spread among four teams, but he acknowledges he has not lived up to his draft status.

"I would say myself," he said during spring work, when asked what has held him back. "I just got to be more mentally strong, I think."

The Eagles' most significant offseason move at corner was drafting Sidney Jones in the second round. Jones had seemed headed for a top-10 first-round spot before he suffered an Achilles tear at Washington's pro day in March. The thinking is that Jones ought to be a key player in a few years, by the time Carson Wentz is really ready to lead the Eagles to the Super Bowl, but he won't play before this October , and could sit out the entire season.

After Jones came another corner in the third round, Rasul Douglas, from West Virginia. Douglas got a lot of attention during the spring for his aggressiveness, and for the fact that he looks like a pro corner – long and lean and graceful.

But as minicamp ended last month, Douglas looked nowhere near ready to start in the NFL.

"He's a young guy that's competing," Jenkins said last month, when asked about Douglas. "We're still trying to get him out of some habits that he has. He's trying to grasp our technique and what the coaches are telling him to do, but one thing that jumped off the tape is that he's got the athletic ability to play corner. He plays really hard, he's got a lot of effort. Those are things that usually [are lacking] in rookies, especially early, when they don't know what they're doing, they're confused."

Douglas was very physical in the spring, to the point that he often did things that would draw flags in games.

Alshon Jeffery gave Douglas some advice as they were running sprints, after Douglas lost a back-and-forth  encounter with Jeffery, Douglas trying to stop a long completion.

Douglas said Jeffery told him: "You can't keep your hand there, to try to keep my arms down. You just got to swipe, let the ref know that you're not holding me, you're allowing me to keep moving in my route. If not, they'll flag that every time."

McLeod said Douglas "takes coaching well, he fights to the end of the play, he's fearless. Those are things that you can't coach, that's just in your heart."

Second-year corner Jalen Mills enters camp as a strong candidate to start, after playing 65 percent of the team's defensive snaps as a rookie. Mills has the size (6-foot, 196), aggressiveness, and mental toughness Schwartz prizes, but he did not show elite quickness as a rookie.

"He's been in games, he's played in big games. He's played good in some games. He's played bad in some games," Undlin said of Mills. "The biggest thing [in the future]  would be that there's a lot more good play than there is good and bad.

"I'm proud of what he did [as a rookie]. He's got to play at a more consistent level … He's got a ways to go, like we all do."

Schwartz said Mills' challenge is "creating that consistency."

Corner is probably the place on the roster where there is the most room for a dark-horse contributor to emerge – Ron Brooks, limited to six games by a ruptured quad tendon last season; Aaron Grymes, a CFL veteran who split time between the roster and the practice squad in 2016; C.J. Smith, Wentz's North Dakota State buddy who appeared in 10 games as an undrafted rookie; or Mitchell White, a former Michigan State player who won the Grey Cup last year with Ottawa of the CFL.

Undlin is in charge of the entire group, but he is the position coach only for the corners; Tim Hauck presides over the safeties. Hauck said last month he thinks improvement will come because McLeod and Jenkins have spent a year in Schwartz's system.

"Last year was a big learning process. What did we want? We didn't know them, what could they do? … [Now] they're used to working with one another, they work really well together," Hauck said.

Jenkins spoke on that subject as well, saying he noticed the holdovers "making better decisions, playing faster, the coverage is getting tighter."

McLeod said he and Jenkins "have grown in our relationship."

On the list of players the Eagles could least afford to lose to long-term injury would be Wentz, of course, and then middle linebacker Jordan Hicks, a leader who lacks a credible backup. Right after them might come Jenkins, who has emerged not only as a Pro Bowl-level player since coming to the Eagles as a free agent from New Orleans after the 2013 season, but also has become one of the league's leading voices against injustice, and a fashion icon with a clothing store.

If anything happens to Jenkins, 2014 fourth-round pick Jaylen Watkins is first in line to step in. Watkins was drafted as a corner and then was released in 2015. He returned later that season and last year transitioned to safety, playing in all 16 games.

At the end of spring work, Hauck acknowledged that Watkins has "got a ways to go," but said that being able to focus solely on playing safety is "definitely going to help him."

Chris Maragos, like Hauck during his playing days, is a special-teams star who can help out at safety in a pinch. Terrence Brooks, the 2014 Ravens third-round pick, got a late start last season after being acquired on waivers Sept. 4. He might have some upside; Hauck said he "brings a physical nature to the game."

On a team that doesn't lack for questions heading into training camp, the secondary has more than its share.