Ducks offensive lineman Matt Pierson was down with a leg injury. Mariota walked onto the field to check on his teammate. As the 285-pound tackle was helped off by his fellow linemen, Mariota patted Pierson on the helmet.
It was a small gesture for sure, but for Mariota actions have always come easier than words. The most dynamic of Ducks is more show than tell.
''It's kind of my nature, I guess,'' the junior quarterback said. ''That's one of my teammates and someone that's been a friend of mine for a few years now. Whenever you see someone go down, it doesn't matter which team it is, it's tough. It's kind of part of the game, but you want to hope that they're OK. For me, I just wanted to make sure he was all right.''
It was a nice thing to do.
The last two Heisman Trophy winners have swept through college football like comets through the night sky. Johnny Manziel and Jameis Winston went from first-year starters to folk heroes (and eventually to anti-heroes in the eyes of many fans) in just a few games.
Mariota, the front-runner to win the Heisman this year, is on a different path. In his third season leading the Ducks, the 21-year-old from Hawaii has only made headlines for his play. And as good as that has been, he is still a bit of a mystery.
Many of Mariota's games are played post-prime time. He is not on Twitter. He doesn't do pregame speeches or sideline rants. He might be college football's best player, but he's not its face.
Make no mistake though, in this corner of the country, Mariota can do no wrong.
They even have a nickname for him. It's not quite as catchy Johnny Football or Famous Jameis.
''Saint Marcus they call him around here,'' said Nico Avila, a 21-year-old senior at Oregon.
That might be a bit much, but consider this: Last week in the lead up to the Stanford game there was a report by Sports Illustrated in which an unidentified NFL scout said there was some concern Mariota was ''too nice.''
This is the closest thing to a controversy involving Mariota.
''I just laughed at it,'' said Mariota, snuggled into sweats and a hoodie after practice earlier this week. Mariota accounted for four touchdowns in a 45-16 victory against the Cardinal last week and No. 5 Oregon will likely need another virtuoso performance by him Saturday when they visit No. 20 Utah.
Mariota is the highest-rated passer in country (187.21). He is tied for third in touchdown passes with 26 and has thrown just two interceptions.
The Ducks scored touchdowns the first three times they touched the ball against Stanford. After each drive, Mariota would head to the far end of the bench area and check in with his offensive linemen. Going down the line he handed out fist bumps and words of encouragement, raising his voice only enough so his teammates could hear him above the din of Autzen Stadium.
He wants his teammates to play with the same poise he does.
''Don't have an emotional roller coaster of a game,'' Oregon center Hroniss Grasu said is Mariota's message. ''Be calm and collected throughout the whole game.
''After a great drive, he comes up, gives us some knuckles. Even if we have a bad drive he'll come up and say, next play, next play.''
Just saying something was a problem for Mariota when he first got to Eugene.
''He's from a culture and from a family where elders are the leaders and you speak when spoken to,'' Oregon coach Mark Helfrich said.
Quiet is not ideal for a quarterback. Helfrich had to force Mariota out of his shell.
''After every play he had to say something to somebody,'' Helfrich said. ''Great snap. Great route. We did that with Marcus just to get everything going. He is such a good guy it was vastly positive. And it grew into where he could push guys and subtly demand things in a great way. His credibility as a leader in our program is awesome.''
Vinny Passas, Mariota's quarterback coach at Saint Louis High School in Honolulu, said the head coach of the team once tried a different approach to get Mariota to be forceful.
''Yell at somebody, get in their face or you got to do 10 gassers,'' Passas recalled the coach saying.
Mariota just started running.
Even now Mariota acknowledges he'd rather play good cop to the coaches' bad cop.
''A lot of guys, they appreciate you just kind of putting your arm around them saying, `OK, this is where I thought you should have been' or `You need to do this during pass protection,''' Mariota said. ''Because during practice they're getting yelled at by the coaches.
''They understand that they did wrong. When you put your arm around a guy and say this is how it could be done, they understand you care about them and you just want the best for the team.''
In football grinders are glorified. Mariota glides around the field, effortlessly it seems. Television cameras find the fiery. Mariota blends in - at least until he has the ball in his hands.
Before Stanford tried to convert a first-half fourth down on Saturday, Oregon players on the sideline exhorted the crowd at Autzen to raise the decibel level. As the Cardinal came to the line, Mariota watched from the edge of the sideline, helmet tilted up on top of his head and his right hand behind his back, inside the fanny-pack style warmer he had tied around his waist.
Mariota tried to get in the spirit of the moment, waving the crowd on with his raised left arm, but it was easy to see he was more focused on the field. His movements had all the enthusiasm and energy of someone trying to signal the waiter for a check.
The Ducks got the stop. Mariota jogged onto the field. Now all eyes were on him - and he brought the fans to their feet the way he does best.
Follow Ralph D. Russo at www.Twitter.com/ralphDrussoAP