Cassandra Mitchell cried three times Saturday.

The first time was when she saw her 18-year-old son, Randy “Duke” Johnson, walk off the bus at Boston College’s Alumni Stadium for his first road trip as a Hurricane.

The next time was when he stumbled, then broke three tackles en route to his first college touchdown – a 54-yarder that preceded a 56-yarder – and pointed both fingers at her from the end zone.

The last time was when he spotted her after the 41-32 UM victory and they “held each other for a good two minutes.

“My heart was in my throat,” said Mitchell, a Miami-Dade corrections officer. “I couldn’t stop boo-hoo crying Saturday.”

Johnson’s 135 rushing yards were the most by any freshman in the nation. His touchdowns were highlighted as No. 6 on ESPN’s Top 10 Plays of the Day. And LeBron James tweeted: “Duke Johnson is the truth out there for the U! True freshman. #speedkills’’

The nation was abuzz about the new kid in college football. But Johnson? All he wanted to do was sleep.

“I’m not sure what time [we got back to Miami] because I was asleep the whole time,” the 5-9, 188-pound Johnson said Monday morning, still looking sleepy in his zipped up black sweatshirt. “Went right to sleep [afterward]. I know I slept for a long time.”

And the past 24 hours? he was asked.

“Resting,” he said, after being “excited from the first snap to the last snap.”

Johnson might flash that shy smile often, but flashy he is not – except for game day. The Miami Norland High alum said his mother has kept him grounded, and he’ll never be the type to draw attention off the field.

“To me it doesn’t really matter if it’s one game or a whole season,” he said. “I’m not going to broadcast myself. I try to stay to myself always and not be into the scenes and spotlight. …I would never let football, or anything, get to my head to where I change who I am.”

Despite the long scores, Johnson said his favorite carry Saturday was on fourth-and-1 from the BC 21. He gained two yards and came out of the play with blood pouring from his nose. Fellow tailback Eduardo Clements scored three plays later.

“When I went to cut and get the first down [safety Jim Noel] grabbed my face mask, lifted my helmet and hit my nose with his hand,” Johnson said. “Some people don’t expect me to be that type of back. They just expect me to run around you and try to make you miss.”

No. 22 Kansas State, Miami’s next opponent at noon Saturday in Manhattan, Kan., just hopes its defense – led by former UM linebacker Arthur Brown – can get him down.

Wildcats coach Bill Snyder was asked Monday morning if he had seen the BC film of Johnson, who also returns kickoffs.

“I have,” Snyder deadpanned. “In fact, I’ve seen too much of it. He is a very dynamic young player, quite obviously. The two long touchdown runs he had demonstrate a variety of different things, that he has good movement and good vision. And beyond it all, he runs faster than most of the people in the world.”

LEWIS ALSO RISING

Though Kansas State has the nation’s No. 35 rushing defense after its 51-9 victory against Missouri State, the Wildcats had similar problems to UM’s with their pass defense. KSU allowed 323 passing yards Saturday, and UM quarterback Stephen Morris has more offensive weapons than just Johnson.

Malcolm Lewis, another freshman, leapfrogged senior Kendal Thompkins on Monday in a promotion to first-team wide receiver. Lewis, out of Miramar High, had four catches for 42 yards and an 18-yard touchdown against BC.

“It was amazing,” Lewis said of his touchdown. “I was proud of myself and wanted to make my mother and family proud, too. It happened pretty fast.”

With the Hurricanes allowing 441 aerial yards Saturday, they likely realize the importance of scoring early and often.

“You’ve got to put up points,” Lewis said, “because you never know what can happen.”