“There are no second acts in American lives,” said F. Scott Fitzgerald, but don’t tell this to Drew Bledsoe.

A career that offered limitless promise in New England and failed to rebound in Buffalo began its third act yesterday, when Bledsoe signed a three-year contract to be the starting quarterback of the Dallas Cowboys (financial terms of the deal were not disclosed). If Bledsoe proves doubters wrong and manages to succeed in his new surroundings, he’ll also save the fourth act of Bill Parcells, the head coach with whom he had his greatest success.

Parcells and Bledsoe arrived in New England together in 1993 and in two seasons took the Patriots from 2-14 to the playoffs. Two years later, they took the Patriots to only their second Super Bowl. In those four years, Bledsoe twice passed for more than 4,000 yards in a season, and looked destined to become one of the greatest quarterbacks in NFL history.

Separated from Parcells, however, Bledsoe deteriorated, along with the New England team around him. His penchant for fourth-quarter comebacks was replaced by one for inexplicable on-field decisions. Then an injury relegated him to the sidelines early in the 2001 season, and he watched as his backup, Tom Brady, achieved what he never could: a Super Bowl title.

Traded to Buffalo, Bledsoe had a strong 2002 but has been mediocre for the past two seasons. This year, his horrid performance in the season’s final week kept a Buffalo team with one of the league’s strongest defenses and top special teams from making the playoffs.

Fans who once saw Bledsoe as an elite quarterback now see him as a mistake prone failure. A former no. 1 pick who played in three Pro Bowls before the age of 26, he was supposed to lead his team to sustained greatness; instead, his biography will always note that it was his backup, an unheralded low-round pick, who fulfilled that promise.

This assessment is more than a little unfair, however. When it comes to quarterbacks drafted no. 1 overall, expectations and reality are two very different things. The players we envision when we think of quarterbacks taken at the top of the draft are all-time greats like John Elway and Terry Bradshaw. But Tim Couch and Jeff George were also drafted no. 1 overall.

Indeed, of the 14 other quarterbacks picked at the top of the draft since 1960, only Elway, Troy Aikman, and Peyton Manning have more Pro Bowl appearances than Bledsoe’s four. And only four of those other quarterbacks taken with the top pick led their teams to the Super Bowl.

Bledsoe’s hope for a dramatic comeback in the third act of his career does have a historical precedent: Jim Plunkett. Like Bledsoe, Plunkett was a no. 1 overall pick by New England who lost a year to injury and found himself replaced by a young backup who quickly became a fan favorite. Like Bledsoe, Plunkett was traded the following season but after disappointing a second team (with two seasons in San Francisco) moved on to a third team. Plunkett then resuscitated his career and led that third team, the Oakland Raiders, to Super Bowl titles in 1980 and 1983. That first title came when Plunkett was 33 years old – the same age Bledsoe will be this fall.

Unfortunately for Bledsoe, the team he joins in Dallas is far different from the one Plunkett joined in Oakland. Plunkett took over a strong Raiders team; Bledsoe’s new team has lost 10 or more games in four of the past five seasons. More importantly, Bledsoe solves a problem that the Cowboys did not actually have.

Though Parcells raised eyebrows last summer by relying on over-the-hill offensive players like Vinny Testaverde, Eddie George, and Keyshawn Johnson, the offense was in no way responsible for the Cowboys’ regression from a surprise playoff team in 2003 to a 6-10 disaster in 2004. The 2003 Cowboys gained 4.9 yards per play, 18th in the NFL; the 2004 Cowboys gained 5.2 yards per play, 16th in the NFL.

In fact, Testaverde completed a higher percentage of his passes than Bledsoe in 2004, and also passed for 7.1 yards per attempt compared to Bledsoe’s 6.5. A nine-year age difference means we can expect Bledsoe to have a better season than Testaverde in 2005, but it is very difficult to envision Bledsoe having a better season than the one Testaverde had in 2004.

In other words, the money the Cowboys will give Bledsoe would have been much better spent on shoring up a defensive unit that collapsed entirely last season. In 2003, the Cowboys allowed 4.3 yards per play, and only Baltimore allowed fewer; in 2004, the 5.5 yards Dallas allowed per play ranked 24th in the NFL. The secondary in particular was a major problem; though safety Roy Williams still played well, the other three starters played opposing receivers as if they carried infectious diseases.

The players Parcells will put around Bledsoe play to his strengths: a talented young running back to take the pressure off his arm, a strong offensive line to protect him in the pocket, and a strong tight end to serve as his main receiver. But slightly above-average passing statistics won’t save Bledsoe’s reputation; winning will. If he isn’t joined by talented defensive players, Bledsoe’s third act will do nothing to turn his detractors back into fans.

Mr. Schatz is the editor in chief of FootballOutsiders.com.