Relax A.J. McCarron. No worries Fitzgerald Toussaint. It's only the biggest game of your life.

The backup Cincinnati quarterback — OK, McCarron's two national title wins at Alabama were probably pretty important, too — makes the first playoff start of his NFL career on Saturday night when the Bengals host the Steelers in the AFC wild-card round. On the other side of the field he'll find Toussaint, who signed to Pittsburgh's practice squad in September before being thrust into a starting role at running back after injuries to Le'Veon Bell and DeAngelo Williams.

Toussaint has run for all of 54 yards during two seasons in the league, 24 coming last week when he came in after Williams left with a busted right foot. Not that Steelers quarterback Ben Roethlisberger is worried.

"That's why statistics don't carry over into the postseason," Roethlisberger said. "It's a new season. It doesn't matter how great of the regular season that he had. Some of the best regular seasons haven't done anything in the postseason and guys who haven't done anything in the regular season have been awesome in the postseason."

Funny he should mention that. Here are five players who went from "Who's That?" to "That Guy" status in the span of four playoff quarters:

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TIMMY SMITH

The resume: Slight. Washington selected Smith in the fifth round of the 1987 draft then promptly buried him on the depth chart behind veterans George Rogers and Kelvin Bryant. He ran for 126 yards in seven games in a limited role but saw his playing time increase late in the year.

The breakout: Smith was serviceable in playoff wins over Chicago and Minnesota but entered the 1988 Super Bowl as mostly an afterthought. Running behind the league's best offensive line against a Denver defense incapable of stopping him, Smith raced for 204 yards, a record that still stands more than a quarter-century later. The image of Broncos safety Tony Lilly futilely chasing Smith to the end zone for a touchdown during Washington's 35-point detonation in the second quarter lives on every winter thanks to NFL Films.

The fallout: Smith arrived in training camp in the next summer as the starter and ran for 100 yards in two of Washington's first three games. He struggled, however, to stay in shape and his health — and production — deteriorated. He was out of football by the end of 1990 and his post-NFL career included a well-publicized battle with drugs.

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ZACK CROCKETT

The resume: Non-existent. Indianapolis took Crockett in the third-round of the 1995 NFL draft and he spent his rookie season blocking for future Hall of Famer Marshall Faulk. Not exactly the recipe for a lot of touches. He had one carry for no yards his rookie year.

The breakout: When Faulk went down in the first quarter of a wild-card game against San Diego, Crockett entered and went off, running for 147 yards and touchdown runs of 33 and 66 yards as the underdog Colts pulled away for a 35-20 upset.

The fallout: Crockett hung around for more than a decade in the NFL, including eight years with the Raiders as fullback and goalline specialist. He finished with 1,701 yards and 47 touchdowns but never came close to that glorious day in Southern California.

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FRANK REICH

The resume: The quarterback's college career at Maryland included the greatest comeback in NCAA history at the time as the Terrapins rallied from 31 down to upset Miami in 1984 before getting one of the best seats in the house in Buffalo behind Hall of Famer Jim Kelly.

The breakout: Reich had thrown just one pass in the playoffs before facing Houston in the wild-card round on Jan. 3, 1993. His pick-six early in the second half gave the Oilers a 35-3 lead and then ... well ... things got weird. For the next two hours Reich threw four touchdown passes and Buffalo somehow pulled out a 41-38 overtime victory that propelled the Bills to a third straight Super Bowl.

The fallout: There was no miracle needed the next week, as Reich led a methodical 24-3 romp in Pittsburgh. Kelly returned for the AFC title game, though Reich filled in during the second half of a blowout at the hands of Dallas in the Super Bowl. Reich hung around until 1998 but ended his career with a 7-15 record as a starter before getting into coaching. Not that it matters in Buffalo, where Reich remains a folk hero.

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JIM O'BRIEN

The resume: A receiver and kicker during his college career at Cincinnati, O'Brien was a third-round pick by the Colts in the 1970 draft but struggled with his accuracy. He made just 19 of 34 (56 percent) of his kicks during the regular season — back in the days when the goalposts were at the goalline — and was just 3 of 7 during the playoffs heading into the 1971 Super Bowl.

The breakout: Like just about every player in the "Blooper Bowl," O'Brien had his issues. A 52-yard attempt in the third quarter came up short. Still, he found himself on the field at the end, making a 32-yarder — shorter than an extra point nowadays — at the gun to give the Colts the title.

The fallout: O'Brien never made more than 69 percent of his kicks during a four-year career that ended with Detroit in 1973. Maybe he was miscast. O'Brien did average 21.8 yards a catch during spot duty as receiver with the Colts and Lions.

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DWIGHT SMITH

The resume: Not bad. The third-round pick out of Akron had four interceptions during his second year with the Tampa Bay Buccaneers in 2002 but was an afterthought on a unit that included Hall of Famer Warren Sapp and Derrick Brooks.

The breakout: Smith scored not one but two pick sixes during Tampa's 48-21 destruction of the Raiders in the 2003 Super Bowl to become an unlikely MVP. Such are the perks of playing center field for one of the greatest defenses in league history.

The fallout: Calling Smith a "one-hit wonder" like Smith or Reich is a stretch, but he never came close to replicating the dizzying heights of that brilliant afternoon in San Diego. His career ended in 2008 with 22 interceptions.

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