Tim Tebow will start at quarterback for the Broncos against the host Miami Dolphins today. (Jack Dempsey/AP)

They won Heisman Trophies and national championships in college, andCam Newton and Tim Tebow entered the NFL facing similar questions about their abilities to become the kind of polished passers who thrive at the professional level.

Newton, who faces the Washington Redskins at home today, quickly answered those questions after he started his career with the Carolina Panthers in record-setting fashion. Watching his breathtaking ability remains as compelling as ever to fans of the NFL, even with the typical rookie-year mistakes that have been part of his play.

Today, Tebow joins him in the spotlight with a headline-grabbing return to Florida, where he played in college, as the Denver Broncos’ new starting quarterback against the Miami Dolphins. In his second NFL season, Tebow will try to show that he has the same capability to succeed as a passer that Newton has demonstrated.

“He’s been a winner at every level,” Steve Mariucci, the former coach of the San Francisco 49ers and Detroit Lions, said of Tebow. “It might not be the way that Tom Brady does it or the way that John Elway did it. But it’s about winning games. He deserves an opportunity to show what he can do.”

There no longer is such criticism about Newton as he readies for just his seventh NFL start. He wasted no time showing what he could do in the NFL when he threw for 422 yards, the most ever by a rookie quarterback in his debut, in the season opener against the Arizona Cardinals.

Newton followed that with a 432-yard outing against the Green Bay Packers, the reigning Super Bowl champions. That quickly, no one was wondering any longer if he could throw accurately enough to be a reliable NFL quarterback, and the Panthers’ decisions to use the top overall choice in the April draft on him and name him the starter seemed fully justified.

“Cam has played much better football than I thought he would after one year of college, after no offseason,” said former Redskins quarterback Joe Theismann. “We’ve seen a great athlete who’s learning to play the quarterback position.”

But there have been growing pains. Newton has thrown nine interceptions, tied with recently benched Redskins starter Rex Grossman for most in the NFL. He is the league’s 25th-rated passer despite ranking fourth in passing yards behind only New England’s Brady, Drew Brees of New Orleans and Green Bay’s Aaron Rodgers. Newton is coming off a three-interception game in a loss to the Atlanta Falcons last weekend.

“With any rookie quarterback, you’re going to see ups and downs,” said Mariucci, an analyst for the league-owned NFL Network. “But his ups have been more impressive than anyone could have hoped for.”

Newton, who won the Heisman and a national title last season at Auburn, also is showing leadership skills. He said during a midweek news conference that he wants to make Carolina one of those places where opponents dread playing. He called the Panthers’ 1-5 record “unacceptable” to him and the organization.

“It’s not just about me,” Newton said. “It’s not about what I do. . . . At the end of the day, you play this game to win. It would be selfish of me to go about each game and say, ‘I’m trying to throw for 400 yards.’ . . . Are you playing this game for individual efforts or are you playing this game to make it to the playoffs, make it to the Super Bowl?”

Other teams are beginning to make adjustments to Newton’s play, said Theismann.

“Now people have some film on Cam,” Theismann said. “Now they’ll get to see what blitzes work, what pressure packages to use, how you go about affecting him in the pocket. But they’re the best 1-5 football team out there. They score points in the high 20s.”

Mariucci called Newton’s quick transition to the pro game a pleasant surprise.

“To predict a rookie is going to go pass for 400 yards or play as well as he’s been playing, you’d be lying,” Mariucci said. “I’ve been impressed. He makes Carolina a dangerous team and he’s only going to get better.”

Across the NFL, it was a week of upheaval at quarterback. The Oakland Raiders traded for Carson Palmer and will start either him or Kyle Boller in place of injured Jason Campbell. The Redskins benched Grossman in favor of John Beck and the Minnesota Vikings turned to rookie Christian Ponder over struggling veteran Donovan McNabb.

Blaine Gabbert has made four starts for the Jaguars and has thrown four touchdown passes and only two interceptions. But he has completed less than half his passes and Jacksonville has lost all four of his starts. Andy Dalton, a second-round choice in April, has fared better. He is the NFL’s 17th-rated passer and the Bengals are 4-2.

But no quarterback will be under more scrutiny than Tebow. He makes his fourth NFL start—and first this season—as he takes over for demoted first-stringer Kyle Orton with the Broncos coming off their bye week.

“He’s a lot like Cam,” Theismann said. “He can buy time with his legs and then make some plays. But this is not a league of pickup football. It’s a game for quarterbacks like Aaron Rodgers and Tom Brady. Tim will bring energy, excitement. But he still hasn’t answered the question everyone has about him: Can he throw the ball effectively enough to win games?”

The contest in Miami matches the winless Dolphins against the Broncos (1-4). Yet there is plenty of excitement as Tebow returns to the state where he won a Heisman and two national championships for the University of Florida. The Gators’ 2008 title-winning team will be honored Sunday. Tebow’s return accounted for an estimated thousands of ticket sales, though the Dolphins and sponsors still had to purchase some unsold tickets to ensure a sellout and avoid a local television blackout.

Tebow made three starts last season after the Broncos made him a surprise first round selection in the 2010 NFL draft. Fox went with Orton as the starter this season to the dismay of many Broncos fans, but made the switch after Tebow nearly engineered a comeback win in a loss to the San Diego Chargers two weeks ago.

“It hasn’t necessarily been a whirlwind,” Tebow said at a midweek news conference. “I just kind of stayed under the radar and kind of came to work every day and tried to get a little bit better.”

Tebow will be without just-traded wide receiver Brandon Lloyd. But now he has his opportunity, and many are watching.

“I’m excited to see him play,” Mariucci said. “I liked him a lot. He had a bye week so that’s good for him. He’ll be in an environment that will be Tim Tebow-friendly. He’s going to a place where there will be 20,000 Tim Tebow jerseys, and honoring the team and all that. But he’s facing a pretty good defense. . . I’m sure there will be growing pains. But it’ll be fun to watch.”