Matt Barkley, the greatest Trojan of them all?

Each time he broke a USC record last season, Matt Barkley humbly acknowledged his place in a Trojans quarterback lineage that includes Heisman Trophy winners and leaders of national championship teams.

Now, Barkley is mulling whether to return for a final college season or join former USC quarterbacks Carson Palmer, Matt Leinart, Matt Cassel and Mark Sanchez in the NFL.

Barkley’s place in USC history is secure because he has played through some of the most severe NCAA penalties ever imposed in college football.

But where does Barkley rank all-time among USC quarterbacks?

“I can’t do it right now,” Coach Lane Kiffin says, “because I think it’s too argumentative.”

Longtime college football broadcaster Keith Jackson agrees.

“Different players surrounding them,” he says. “And, for some, different offenses.”

No matter, says former Trojans All-American receiver Keyshawn Johnson.

He calls Barkley “the best ever to play here.”

Agree or not, longtime Trojans observers universally acknowledge that Barkley is, as former coach John Robinson put it, “one of the most important” players in Trojans lore.

Barkley started as a true freshman before becoming the poised face of the program when the NCAA handed down sanctions that included a two-year bowl ban and three years of scholarship reductions. He has nimbly handled hundreds of interviews in the 18 months since and led the Trojans to a 10-2 finish this season.

“We’ve never had a guy that deserves to ride off on the white horse as much as him,” Robinson says, “just because of the circumstances.”

Statistically, Barkley ranks behind Palmer and Leinart, both of whom spent five seasons at USC.

Last season, Barkley established a Pac-12 record for touchdown passes and a school record for completion percentage. He also set single-game USC records for touchdowns, completions, passing yardage and total offense.

But Barkley, a three-year starter, has never been voted to the first-team all-conference or All-America teams. He has not led the Trojans to a conference title, though USC would have played in the inaugural Pac-12 Conference championship game this season if not for NCAA sanctions.

Nor has he won a national title or been a Heisman finalist.

“It’s not all about the Heisman,” says former quarterback Paul McDonald, who led the Trojans to a national title in 1978 and now works as an analyst on USC radio broadcasts. “It’s all about the rings. It’s a little unfair for a quarterback, but that’s the way it is.”

By that measure, Leinart is the best.

He helped the Trojans to an Associated Press national title in 2003 and a Bowl Championship Series crown in 2004, when he won the Heisman. He was a Heisman finalist again in 2005, when he led the Trojans to the BCS title game.

Palmer won the 2002 Heisman and led the Trojans to the first of seven consecutive BCS bowl games.

Rodney Peete was a Heisman finalist in 1988.

Pat Haden played on two national championship teams, one as a starter. Pete Beathard, Steve Sogge, Mike Rae and McDonald also led the Trojans to national titles in the modern era.

Tom Kelly, who broadcast USC games from 1961 to 2002, says Barkley’s achievements are noteworthy because “I’m not sure he had the same kind of experienced talent around him that some of the other quarterbacks who won championships did.”

Todd Marinovich, Rob Johnson, John David Booty and Sanchez did not win titles, but they are among other quarterbacks who had notable statistical careers or seasons.

NFL draft guru Gil Brandt says Barkley compares favorably to Sanchez, who was the fifth pick in the 2009 draft after one season as a starter. But Brandt rates Barkley higher than all but one USC quarterback.

“I’d probably put him over Leinart,” he says. “I don’t think I could put him over Palmer.”

Palmer was the first pick in the 2003 NFL draft.

Barkley is projected to be the second quarterback taken in April if he opts to turn pro. Stanford’s Andrew Luck is the presumed No. 1 pick after returning to lead the Cardinal to a second consecutive BCS bowl game.

If Barkley stays in school, he’ll be a Heisman front-runner and USC will rank among the top BCS title contenders.

If he won the Heisman and the Trojans won the championship…

“He’d be top of the food chain,” McDonald says.

And not just among Trojans quarterbacks, according to Haden, the Trojans’ athletic director.

“I think he would maybe go down as the greatest Trojan of them all,” he says.

No need for a qualifier, says Johnson, the top pick in the 1996 NFL draft.

If Barkley comes back, graduates and leads the Trojans to a national title, Johnson says, “he goes down as the greatest Trojan ever.”

“Just imagine being the No. 1 Trojan of all time,” he says. “That’s better than being in the Pro Football Hall of Fame.”

gary.klein@latimes.com