The Navy football team lined up to stretch before a preseason practice last month. (Toni L. Sandys/The Washington Post)

When Navy quarterback Tago Smith left last Saturday’s season opener early in the second quarter with an apparent season-ending knee injury, backup Will Worth entered without having taken a snap at the position all last year. The senior had played only as the holder on field goals and extra point attempts, but his dearth of in-game experience didn’t invoke panic on the Midshipmen sideline.

Worth simply executed the plays in the same manner as he had been instructed during practice, leading to his eight-yard touchdown run two snaps later on the way to a 52-16 win against Fordham. Worth accounted for two touchdowns and did not commit a turnover.

Worth’s glowing debut, albeit against a lower-division opponent, came as little surprise to Coach Ken Niumatalolo or offensive coordinator Ivin Jasper given the extensive preparation the backup quarterbacks receive throughout the season. It’s an amenity unique to the service academies because they don’t offer athletic scholarships and thus are not bound by the roster limit of 105 players at other major college programs.

This year, Navy lists 166 players on the roster on its official website. Army has 144, according to its website, and Air Force lists 95, though the Falcons don’t include freshmen on their roster. The sheer enormity allows the coaching staff to run multiple huddles during practice and generally provides the reserves as much opportunity as the starters to learn the nuances of the triple-option offense.

Navy quarterbacks — there are nine listed on the roster on the team’s official website — warm up before a preseason practice. (Toni L. Sandys/The Washington Post)

That in part explains how Navy has been able to win consistently even when untested quarterbacks ascend to the starting job.

“We feel fortunate to have Will. He has been in our system, just like Tago has,” Niumatalolo said. “Obviously Ivin is coaching those guys, and he knows exactly what he’s doing. Will is a smart kid. You’ve seen him in practice, so he knows what we’re doing. He knows our checks. He knows how to run our offense. You feel good about that.”

The Midshipmen even leaned on a freshman quarterback last weekend for relief duty in one of the most implausible scenarios in program history. Soon after Smith tore an anterior cruciate ligament, Malcolm Perry came out of the stands, changed into his football uniform in the locker room at halftime and played the fourth quarter. Before the game, Perry had marched on with the brigade in his dress whites.

Perry began the season as the fourth-stringer but was pressed into service because regular No. 3 Zach Abey was serving a one-game suspension for an unspecified violation. When Smith departed the game for good, Navy was down to one quarterback on the sideline until Perry’s quick change.

Abey is back this week as Worth’s primary backup for Saturday’s American Athletic Conference opener against Connecticut (1-0) at Navy-Marine Corps Memorial Stadium.

“It’s always been the next man up, for people to continue to be ready at all times,” Worth said. “Just like that, things can happen. We saw that on Saturday. Our hearts break for Tago, but we need to keep this rolling like we started on Saturday.”

Perry had participated in the junior varsity game the night before the Fordham game after missing the first three days of practice because of an illness. He had no inkling the season opener would provide his first varsity experience, but like Worth, Perry also was comfortable directing the offense because of the considerable number of snaps he had taken in practice.

Although Navy fields a junior varsity team, all football players at the academy are part of a single roster. Coaches determine which players participate in the junior varsity games — there are five this season, against post-secondary prep schools and junior college-level programs. The junior varsity roster is made up of mostly freshmen and sophomores, with an occasional junior based on need at a particular position. Seniors do not play on the junior varsity.

Many players who participate with the junior varsity also are in uniform for the varsity games. Those players stand a chance to play in the varsity games if there’s a lopsided result, such as in last weekend’s season opener.

“Will, in the first game, he was talking to me and was like, ‘You never know,’ ” Abey said. “Unfortunately what happened to Tago, it’s hard because he’s such a great kid. He’s been waiting for it, but at the same time, Will has been waiting for it the same way. They’re both the most selfless guys, but we’re definitely taking another step.”