Stanford had returned a second-quarter interception for a touchdown.
"Coach D was just giving me this look and I was hoping he wasn't going to be super upset and say something to put me down," Cook said.
But the ensuing exchange repeated a seasonlong script.
"You good?" Dantonio said.
"Yeah, I'm fine," Cook answered.
The two traded a fist bump, felt better about the situation, and then went their separate ways.
"Everything," Cook said, "was good after that."
Cook came back on the ensuing possession and passed for a touchdown, propelling Michigan State to a 24-20 come-from-behind victory in the 100th Rose Bowl game.
Cook, a third-year sophomore in his first season as a starter, completed 22 of 36 passes for a career-best 332 yards and two touchdowns.
"I could see it coming as we continued on through the season," said Dantonio, whose team finished 13-1. "He just continued to elevate his play with experience.
"We are in a big-time environment. We're at the Rose Bowl playing the No. 5 team in the nation. There is no bigger prize, really. How far can you go to reach that level emotionally? And he just continued just to impress."
Cook's two-yard touchdown pass to fullback Trevon Pendleton pulled Michigan State to within 17-14 just before halftime.
"Any time you can end the half on a touchdown, that gives you so much momentum," Cook said. "I think that was kind of like the turning point for the game."
His 25-yard touchdown pass to Tony Lippett early in the fourth quarter put the Spartans ahead, 24-17.
Cook's performance was far from seamless.
In the first quarter, Stanford linebacker Kevin Anderson dropped what looked like a certain interception.
Later in the quarter, Anderson picked off a short pass by Cook and returned it 40 yards for a touchdown to put the Cardinal ahead, 17-7.
Stanford cornerback Wayne Lyons dropped a ball, and another potential interception was nullified when Stanford safety Jordan Richards was penalized for holding.
But Cook pushed on.
"He's got a lot of poise," Stanford linebacker Shayne Skov said. "Especially in the pocket, he's able to extend plays and find open guys. … We tried to get after him, but at the same time I think he remained calm and made plays when he needed to."
Said Dantonio: "He does not get rattled."
Michigan State tied the score with a field goal early in the third quarter, and the teams then traded possessions five times before the Spartans returned a punt to the Cardinal 27-yard line early in the fourth quarter.
On third down, Cook connected with Lippett over the middle to give the Spartans their first lead.
The 6-foot-4, 218-pound Cook spoke this week about the stress he felt during spring practice and fall camp, when he was trying to win the starting position. He broke through in the third game against Youngstown State and bounced back after he was pulled from the Spartans' only loss, against Notre Dame.
Cook led the Spartans to 10 consecutive wins and finished the season with 22 touchdown passes and six intercepted passes.
"It's just been a roller-coaster ride," he said. "The stuff you dream about as a kid."