For much of the 2017 NFL season, the Eagles flew high above the pack in large part due to the play of quarterback Carson Wentz. The second-year quarterback performed at an MVP level, cutting his rookie interception total in half while more than doubling his number of touchdown passes and leading Philadelphia to an NFC-best 11-2 record.

But disaster struck late in the season. During a Week 14 clash with the Rams, Wentz suffered a season-ending knee injury, throwing the Eagles' title hopes in doubt. In entered Nick Foles, a journeyman signal-caller who hadn't started a meaningful game for Philly in three seasons.

While Foles hasn't matched Wentz's overall consistency, he has more than held his own. He shocked many by throwing four touchdowns in his first start of the season and played well enough to help the Eagles outlast the Raiders on Christmas to secure the No. 1 seed in the NFC. Foles raised his play in the postseason, delivering an all-time great performance in the NFC title game to send the Eagles to the Super Bowl for the first time in over a decade.

On Feb. 4, Foles will become the rare backup quarterback to start in a Super Bowl. How rare? By defining reserve QBs as only those who did not start their team's opener in the same season they started in the Super Bowl -- a standard that filters out injury replacements such as Kurt Warner who ended up starting in Week 1 -- only six players have pulled it off.

Craig Morton

Dallas Cowboys, Super Bowl V

Though Morton fits the parameters of a backup quarterback starting a Super Bowl, that label doesn't do him justice. Cowboys head coach Tom Landry spent the season alternating quarterbacks, and Roger Staubach just happened to get the nod for the opening week of the 1970 season. Morton went on to start 11 of the team's 12 games that year, with Landry giving him the start for Super Bowl V due to concerns Staubach would deviate too far from his game plan.

That game plan certainly did not involve the three interceptions Morton threw, all in the fourth quarter. Those turnovers turned a 13-6 Cowboys lead into a 16-13 defeat. The following season, Landry ceased alternating quarterbacks and handed the job to Staubach full time, and the Cowboys won their first championship as a result.

Though history paints Morton as the loser of one of the greatest QB controversies in NFL history, he produced a more-than-respectable career. After the Cowboys traded him in 1974, Morton went on to start over 100 games, including Super Bowl XII with the Broncos. Of course, that contest pitted him against Dallas and Staubach, adding to the pain of a 27-10 defeat.

Vince Ferragamo

Los Angeles Rams, Super Bowl XIV

Few thought the Rams would compete for a title when the 1979 season began. Even fewer believed in them after starting quarterback and Los Angeles football legend Pat Haden broke the pinky finger on his throwing hand during a Nov. 4 game with the Seahawks. The injury opened the door for Ferragamo, a mostly anonymous player with no career starts to his name.

Ferragamo didn't light up the box score during his time as the starter, completing fewer than half his passes and throwing twice as many interceptions as touchdowns. Yet the Rams won all but one of his starts and limped into the playoffs with a 9-7 record.

The Rams' play improved in the postseason, especially that of Ferragamo. He threw for over 200 yards and three touchdowns for the first time in his career during a first-round matchup with the Cowboys and played largely mistake-free in a win over the Buccaneers. During the final minute of Super Bowl XIV against the Steelers, Ferragamo had the ball with a chance to win but threw a critical interception on a pass intended for wide receiver Ron Smith. That turnover cost the Rams the game.

Ferragamo's career followed a winding path in the years following the Super Bowl. He returned in 1980 as the Rams' starting quarterback, and delivered his best season as a pro. He turned the big year into a large contract with the Montreal Alouettes of the Canadian Football League. That marriage lasted one forgettable season with Ferragamo returning to Los Angeles in 1982. He never regained his peak form and spent the rest of his career hopping between teams.

Doug Williams

Washington, Super Bowl XXII

Washington never intended to start Williams at quarterback on its way to Super Bowl XXII. Jay Schroeder, the talented but often abrasive veteran, was picked for the Pro Bowl the previous season and looked poised to build on that success, leaving Williams to handle mop-up duty. Instead, Williams replaced an injured Schroeder in Week 1, delivering a magnificent 272-yard, two-touchdown performance in relief.

Schroeder's injury didn't sideline him long, and by Week 3 he reclaimed his job despite mostly stellar play from his replacement. Williams started only one more game the rest of the regular season, and while he continued to perform well, head coach Joe Gibbs decided to stick with Schroeder under center.

However, Schroeder failed to deliver in the season finale, convincing Gibbs to reinsert Williams and ride with him the rest of the way. It proved to be one of the great decisions in the Hall of Fame coach's career as Williams guided Washington through the NFC playoff field before passing for 340 yards and four touchdowns in a decisive 42-10 victory over John Elway's Broncos in the Super Bowl.

Williams struggled to reach those highs again for the rest of his playing career. His pedestrian play in 1988 contributed to Washington's losing record, and he started just two games the following season due to injuries. Williams called it a career after the '89 season.

Jeff Hostetler

New York Giants, Super Bowl XXV

The 1990 Giants had the look of a title contender. Led by head coach Bill Parcells and All-Pro pass rusher Lawrence Taylor and Pro Bowl quarterback Phil Simms, the team appeared ready to dominate the NFC East and storm the postseason.

That left little work for Hostetler, the team's backup quarterback. With Simms entrenched as the starter, Hostetler spent time at other positions. At one point, he even asked for a trade, though Parcells denied his request. That decision proved wise when the Giants lost Simms to a broken foot in Week 15. In came Hostetler, who helped the team to back-to-back wins during the final two weeks of the season.

The Giants didn't air out the ball with Hostetler at the controls, choosing instead to refocus the offense on fellow injury replacement Ottis Anderson and the ground attack. That approach allowed New York's sterling defense to extend the winning streak into the playoffs, including a win in Super Bowl XXV.

After the Super Bowl, Hostetler started most of the next two seasons for the Giants. He then joined the Raiders in Los Angeles, where he earned his only Pro Bowl selection. Hostetler later landed in Washington where he played out the final years of his career as a reserve.

Trent Dilfer

Baltimore Ravens, Super Bowl XXXV

Dilfer entered the NFL as a highly touted quarterback prospect, selected by the Buccaneers with the No. 6 overall pick. While he earned a trip to the Pro Bowl during his fourth season, he otherwise struggled, throwing 20 more interceptions than touchdowns during the rest of his tenure in Tampa. When his contract expired, the Bucs let him walk.

Dilfer resurfaced in 2000 with the Ravens as a backup to Tony Banks. Though the team got off to a 5-1 start, the offense couldn't seem to get its footing with Banks under center. Head coach Brian Billick made the switch to Dilfer for the seventh game of the season and didn't look back.

The Ravens didn't put many points on the board with Dilfer, scoring 30 or more points only twice after he replaced Banks. Still, the conservative style complimented the team's historic defense. Dilfer gave Baltimore just enough points to allow Ray Lewis and company to take care of the rest. The marriage culminated in a victory over the Giants in a dominant win in Super Bowl XXXV.

After taking home the Lombardi Trophy, the Ravens decided to replace Dilfer with Pro Bowl quarterback Elvis Grbac. Grbac lasted just one year in Baltimore before retiring, while Dilfer went on to start 29 games for the Seahawks, Browns and 49ers.

Tom Brady

New England Patriots, Super Bowl XXXVI

As with several of the other quarterbacks to start a season holding a clipboard and end it starting in the Super Bowl, an injury opened the path to Brady's ascension. Drew Bledsoe, a former No. 1 overall pick and the Patriots' franchise player, took a brutal hit during the second week of the season, resulting in internal bleeding and a trip to the hospital.

Bledsoe eventually recovered from his injuries, but not before Brady had pried the job away for good. Outside of pinch-hitting for Brady in the AFC title game, Bledsoe never played a meaningful down for the Patriots again.

Brady had only modest production during his first Super Bowl, completing less than 60 percent of his passes for 145 yards and a touchdown. But the second-year quarterback didn't make any backbreaking mistakes, allowing a solid Patriots defense to force multiple turnovers from the "Greatest Show on Turf" Rams. Those plays, along with a last-second field goal from Adam Vinatieri, tilted the outcome in New England's favor.

Brady, of course, had yet to attain legendary status at the time of Super Bowl XXXVI. Neither had head coach Bill Belichick, who remained better known for his disappointing five years with the Browns than his previous title-winning stints as defensive coordinator for the Giants. Both player and coach permanently altered their path toward football immortality by upsetting the Rams, winning the first of five Lombardi Trophies together.

They'll play for a sixth against Foles and the Eagles.