Florida State's Karlos Williams will miss Saturday's ACC championship game against Georgia Tech as the senior tailback won't be cleared to play after suffering a concussion last week, school officials said.

Williams, who suffered the concussion early in the No. 4 Seminoles' victory against Florida, has rushed for 609 yards and 10 touchdowns this season. He is averaging 4.4 yards per carry.

Freshman speedster Dalvin Cook will start against No. 11 Georgia Tech (10-2, 6-2, No. 12 AP) on Saturday. Cook, who rushed for a career-best 144 yards against the Gators while filling in for Williams, has 728 yards this season.

Cook only needs 161 more yards to break FSU's 33-year-old freshman rushing record, which was set by Greg Allen (888) in 1981.

"There's not enough positive things you can say about Dalvin," said senior center Cameron Erving, a two-time winner of the ACC's best blocker award. "He's been very, very vital to our success."

Georgia Tech coach Paul Johnson ranks Cook among the best backs he's had to prepare for all season, comparing him to Georgia's Nick Chubb and Sony Michel.

"He's at least that caliber," Johnson said. "He's got great speed and really catches the ball well."

The Associated Press contributed to this report.