Three times the Eagles demoted their safeties, and each time Jarrett was passed over.
During the preseason, Allen was benched when it was clear his surgically repaired knee wasn't ready; he was replaced by Jarrad Page. In Week 3, Kurt Coleman took a seat for his shaky play, and Allen was back in the starting lineup. Three weeks later, Coleman got another chance after Page became an increasing liability.
"I was never frustrated - it's all about learning," Jarrett said Thursday as the Eagles prepared for Sunday's game against the Arizona Cardinals. "We didn't have [spring practices]. I had a slow start."
When Allen suffered a concussion in the first quarter of Monday night's game against Chicago, however, Jarrett got the nod over Page. After dressing for several weeks and playing on special teams, his time had finally come.
Eagles defensive coordinator Juan Castillo said that his backup safeties typically get a handful of repetitions with the first team during practice. But Jarrett was being thrown into a tough situation - the Bears were driving for a touchdown on their opening drive when Allen went down - and he comported himself just fine.
"He had a solid game," Castillo said.
Jarrett recorded three solo tackles and didn't give up a big play, but the Cardinals now have film on the rookie and know that he is likely to start. Allen hasn't practiced yet this week and has yet to see an independent neurologist who can clear him to return.
So it's going to be Jarrett, who Castillo said has been taking all the first-team reps this week at practice. It's the perfect game for the rookie to make his first start. The 2-6 Cardinals are likely to be without injured starting quarterback Kevin Kolb, and they enter with the 25th-ranked offense in the NFL.
Jarrett, 22, was inactive for three of the first four games this season, which seemed a few too many for a second-round pick, and one who plays a a position at which the Eagles were weak.
"We all have expectations, and you want to reach your own and the ones the coaches have for me," Jarrett said. "I know the expectations are high."
Coleman could sympathize. He missed all of the spring practices last year because of Ohio State's late semester.
Still, when Allen missed his first game because of injury last season, Coleman - like Jarrett this season - had to jump in and start in his first season.
"It's something that you hope for," Coleman said. "You're backing up at practice and you're thinking, 'Man, I hope it's my time.' When you get out there you want to slow things down. But your excitement and adrenaline is pumping so much, things start to get a little cloudy."
At Temple, Jarrett was like a fourth linebacker. The big hitter was often asked to help out against the run, but his cover skills suffered as a result. In the Eagles system, both safeties are interchangeable and need to be as adept at stopping the run as they are defending the pass.
And then there's the extra responsibility of calling out lane assignments, something Jarrett said was perhaps the hardest to learn.
"As the safety, you're the quarterback of the defense," he said. "You have to know your assignment inside and out as well as the corners and the linebackers, because on run plays you have to know where you fit."
For at least one game, he'll finally fit in as the starter.
Extra points. Guard Evan Mathis (turf toe) didn't practice for the second straight day. King Dunlap has been taking most of the practice reps in his place at left guard, but offensive coordinator Marty Mornhinweg said rookie Julian Vandervelde also took turns there. . . . Cornerback Asante Samuel was limited at practice because of the groin injury he suffered against the Bears. Juqua Parker (high-ankle sprain) was also limited. . . . Defensive end Jason Babin ripped Bears offensive coordinator Mike Martz, saying the Bears used a dangerous block to take him out on a play early Monday. "I'd assumed [Bears coach] Lovie Smith has enough professionalism to not do something like that," Babin said.
Contact staff writer Jeff McLane at 215-854-4745, firstname.lastname@example.org or @Jeff_McLane on Twitter.
Staff writer Jonathan Tamari contributed to this story.