Lattimore sprained his left ankle early in the second half of South Carolina's 31-28 loss to Kentucky. The Gamecocks were ahead 28-10 when Lattimore got hurt.
Spurrier said Wednesday that Lattimore had not practiced this week and was doubtful to face the Commodores (2-4, 1-2).
"Kenny's a very good back who just hasn't had the opportunity to play much this year. So he's going to start the game and hopefully go a long way," Spurrier said. "If Marcus has a miraculous recovery and says he feels fine, we'll see about getting him in there."
Lattimore worked on the sidelines during Wednesday's practice, jogging and even running a few sprints to test the ankle. He said he felt about 80 to 85 percent.
"It's feeling way better than it did Saturday night," Lattimore said.
Lattimore said if the ankle feels good enough, he'd like to get a few carries Saturday.
But he is also excited to see Miles getting the start, saying the sophomore hasn't let the competition for playing time get in the way of helping Lattimore learn the ropes in the SEC.
Star wideout Alshon Jeffery, tied for the SEC lead with 40 catches, missed practice Tuesday with a pulled muscle in his stomach but should be OK for Vanderbilt, Spurrier said.
Miles was South Carolina's leading rusher a season ago with 626 yards. Through six games, Lattimore has gained 538 yards and rushed for 10 touchdowns. Miles, a sophomore from Lawrenceville, Ga., has only rushed in two games this year and all but one of his nine carries coming in the fourth quarter of decisive wins over Southern Miss and Furman.
That's a far cry from the end of last season when Miles' powerful runs gained 114 yards and helped lock down a 34-17 victory over rival Clemson.
Senior Brian Maddox has been Lattimore's primary backup and South Carolina's second leading rusher.
Miles' role changed with the addition of Lattimore, one of the SEC's top freshman this season. Through it all, Miles has continued to work hard and prepare for a chance, Spurrier said.
"Kenny Miles has had a wonderful attitude about his situation," the coach said. "He's not complained one bit. He's going to get his chance."
South Carolina's offense has been built in part around Lattimore, the 5-foot-11, 215-pound dynamo from Byrnes High who was considered one of the nation's best running back prospects last winter.
He broke out in his first SEC game with 182 and two TDs as the Gamecocks defeated Georgia 17-6. Lattimore had 93 yards and two rushing touchdowns against Alabama's stingy defense in South Carolina's 35-21 upset two weeks ago.
Lattimore was on his way to a similar performance last Saturday night at Kentucky before his injury, rushing for 71 yards and two touchdowns as South Carolina led 28-10 at halftime.
The Gamecocks offense went to the sidelines along with Lattimore, registering only 95 yards the rest of the way after putting up 369 the first two quarters.
South Carolina doesn't count on just one player to win, receiver Tori Gurley said.
"Marcus is a great player, but we're a total team," Gurley said. "Brian Maddux and Kenny Miles and the other backs are ready to step up and make plays."