"His best qualities are never talked about," he said. "The qualities are such that people will pay good money for him some day."
When asked what Luck's best quality might be, Harbaugh got a little twinkle in his eye and smiled. "I'm not going to tell you . . . maybe in three weeks . . . or 18 days."
Perhaps the simplistic answer is Luck wins, period. The bottom line for any quarterback, according to previous Harbaugh dissertations, is leading the team to victory.
In Luck's first 21 starts for Stanford (5-1, 8-1), he's produced 16 victories. He'll be looking to add to that when the seventh-ranked Cardinal visits Tempe for a Pac-10 game against Arizona State at 4:30 p.m. (PST) Saturday.
Of Luck's name in reference to the Heisman Trophy, perhaps Harbaugh offered another clue. "He's not concerned about it at all," he said. "He's played great all year and he's improved every week."
Luck's answer was to have no answer.
"I'm just worried about how to keep the offense going in the right direction," Luck said. "My comfort zone grows each week but I also get to line up behind our offensive line."
Sometimes talking to Luck is like talking to the nerdy guy who lives down the hall. You just don't quite know what to make of him. He's so 'aw-shucks' it's almost as though he was putting one over on you.
When his teammates start lining up in his support, though, you begin to realize Luck really might be a throwback to the days of the old dime-store magazine and boy-next-door-makes-good stories.
"He is incredibly humble," Stanford linebacker Shayne Skov said when asked about Luck's best quality. "He believes he doesn't deserve all the attention. He thinks he's not good yet. He never truly rests. He will always continue to get better. That's who he is as a player."
Luck may still not feel comfortable talking to a room full of media but he'll never let on. It's likely the same way when he's in a huddle or looking out over the defense as he approaches the line of scrimmage. He's in the moment and there are no other distractions.
He takes the blame for every offensive miscue and deflects kudos toward his teammates. The son of a former NFL quarterback, he's more 'average guy' than the average guy walking down Main Street of some small town in the Midwest.
"He's a great leader and humble," Cardinal safety Delano Howell said. "He puts the team ahead of himself."
Statistically he's having an outstanding year. Luck ranks seventh in the nation in passing efficiency with a rating of 163.37. Stanford ranks fifth in scoring offense, averaging 42.33 and Luck ranks tied for fifth in Points Responsible For at 17.56 per game.
Harbaugh points to Third Down Efficiency, at which Stanford leads the nation with a 58.47 percent success rate. Stanford has scored 51 times in 54 trips into the red zone, the fourth best percentage in the nation, and the best among teams with at least 40 visits.
"A lot of that has to do with the quarterback," Harbaugh said. "The one measure of a quarterback is how he performs on critical plays, and making critical throws. Third down is a separator for quarterbacks statistically."
Luck has 370 rushing yards this season, second only to Stephan Taylor, and already the highest total by a Cardinal quarterback in school history. Of course, he's more than his stats.
"He's taking his leadership role to another level," Stanford receiver Chris Owusu said. "He's constantly trying to learn about the next opponent and he works on his own skills."
Harbaugh could have been stalling for time. Who could blame him? Explaining the ineffable is difficult.
NOTES: A win Saturday would give Stanford its best 10-game start since 1951 and its longest winning streak since the 1996 season . . . The Cardinal is 3-10 in Sun Devil Stadium and has not won there since 1999 . . . Stanford has punted 20 times this season, second fewest behind Boise State's 17 . . . The 16 Cardinal players who have scored at least one touchdown ties for most in the nation with Central Florida and Utah . . . Stanford has scored 380 points this year, already the fourth-highest total in school history. Last year's team holds the record with 461 . . . Stanford averages 223 rushing yards, second in the Pac-10 and 12th nationally. It's also 18.1 yards per game ahead of last year's pace after nine games.