Church was named to the Pittsburgh Tribune-Review's "Terrific 25" team, second-team all-state Class AAAA, first-team Western Pennsylvania Interscholastic Athletic League-East honors, and played in the Big 33 Football Classic.
As a freshman, he registered 76 tackles (second on the team) and 4 interceptions, including 2 returned for touchdowns (tied school record).
[5][6] Throughout training camp, Church competed for a roster spot as a backup safety against Michael Hamlin, Patrick Watkins, Akwasi Owusu-Ansah, and Danny McCray.
[7][8] Head coach Wade Phillips named Church the backup strong safety, behind veteran Gerald Sensabaugh, to start the regular season.
On November 9, 2010, the Cowboys fired head coach Wade Phillips after a 45–7 road loss to the Green Bay Packers and falling to a 1-7 record.
Church returned to training camp in 2011 and competed for a role as a backup safety against Andrew Sendejo, Danny McCray, Akwasi Owusu-Ansah, and Michael Hamlin.
New head coach Jason Garrett named him the backup behind Gerald Sensabaugh and Abram Elam to start the regular season.
On December 11, 2011, he earned his first NFL start and recorded two solo tackles before leaving the eventual 37–34 loss to the New York Giants in the third quarter with a shoulder injury.
Two weeks later, he made a season-high three solo tackles in a 16–10 victory against the Tampa Bay Buccaneers, but left in the third quarter after sustaining a torn Achilles.
[17] Church finished his last season under defensive coordinator Rob Ryan with six combined tackles (four solo) in three games and three starts.
[18] Throughout training camp, Church competed for the job as the starting free safety against rookie J. J. Wilcox and Matt Johnson after it was left vacant by the retirement of Gerald Sensabaugh.
[20] On October 20, 2013, Church recorded five combined tackles, broke up a pass, and made his first NFL interception off quarterback Matt Barkley during a 17–3 road victory over the Philadelphia Eagles.
[22] During Week 12, Church recorded eight solo tackles, deflected a pass, and returned an interception by Eli Manning for a 45-yard gain during a 35–28 road victory over the New York Giants.
Two weeks later against the Buffalo Bills, Church recorded seven combined tackles, but left the eventual 16–6 road loss in the fourth quarter after breaking his arm.
[28] During a Week 6 30-16 victory over the Green Bay Packers, Church had five tackles, a forced fumble, a pass defended, and a third-quarter interception.
[34] During a Week 4 23-20 road loss to the New York Jets, Church made six combined tackles and sacked quarterback Josh McCown once.
In the next game, Church recorded five combined tackles, deflected a pass, and returned an interception by Ben Roethlisberger for a 51-yard touchdown during a 30–9 road victory over the Pittsburgh Steelers.
Church finished his first season with the Jaguars with 72 combined tackles (58 solo), eight pass deflections, four interceptions, 1.5 sacks, and a touchdown in 16 games and starts.
He drew criticism and received a personal foul after delivering a hit to tight end Rob Gronkowski's head during the second quarter.