COLUMBIA — South Carolina will have to play one of the season’s most important games without one of its best players.

The Southeastern Conference on Monday suspended USC free safety D.J. Swearinger for Saturday’s 3:30 p.m. home game against Missouri — the result of what the league called his “flagrant and dangerous” hit in last Saturday’s 49-6 win over Alabama-Birmingham.

The suspension is a huge loss for the seventh-ranked Gamecocks (3-0, 1-0 SEC) as they prepare for their second game against an SEC East Division opponent. Swearinger, a senior, is a third-year starter who rarely comes out of games. The Gamecocks have no other proven free safeties.

The depth chart lists his backup as senior walk-on Jared Shaw. He was impressive at times as a cornerback during spring practices, but has rarely played. On Saturday, Shaw drew a roughing-the-punter penalty on the play that preceded Swearinger’s hit.

Entering the preseason, the No. 2 free safety was redshirt freshman Sheldon Roy-ster, a former highly regarded recruit who was the fifth-highest rated prospect in USC’s Class of 2011, according to Rivals.com. But Royster decided to transfer last month and wound up at Rutgers.

Through three games, Swearinger has 10 tackles (nine solo), an interception, three pass breakups (tied for the team lead) and a fumble recovery that he returned 65 yards for a touchdown against UAB. He is the secondary’s only returning starter from last season. He and sophomore strong safety Brison Williams are both responsible for getting the defense’s backfield lined up before the snap, but Swearinger is the secondary’s most vocal leader.

The play for which he was suspended happened with 5:46 left in the third quarter Saturday, when Jonathan Perry threw a pass over the middle intended for Patrick Hearn, who reached up for the ball.

As the ball hit Hearn’s hands, Swearinger launched himself forward and made facemask-to-facemask contact with Hearn, causing a pass breakup. The hit was not late, but the helmet-to-helmet contact resulted in a 15-yard personal foul penalty. Referee Ken Williamson specified it as “contact above the shoulders against a defenseless player.”

USC coach Steve Spurrier said Sunday that he thought Swearinger’s hit “was a lot similar to the hit Justice Cunningham took at Vanderbilt.” That hit, in the season opener, resulted in a 15-yard personal foul but no suspension.

USC said Spurrier would not comment on the suspension Monday, but will address it today at his weekly news conference.

Later Monday, the SEC released an additional statement regarding the differences between Swearinger’s hit and the hit by Vanderbilt cornerback Andre Hal on Cunningham.

The statement read: “On replay, although contact was made to the receiver’s helmet, the primary contact from the Vanderbilt defender was to the shoulder area. The Vanderbilt defender never lowers his head and the contact is made with his facemask up, looking at the South Carolina receiver. It was a foul because there was glancing contact to the receiver’s helmet.

“In the UAB contest, based on video replays, the contact was initiated by a slight launch of the defender into the receiver and the primary contact was targeted directly into the receiver’s facemask.”

Earlier Monday, the SEC said Swearinger’s hit violated the section of the NCAA rule book that reads: “No player shall target and initiate contact to the head or neck area of a defenseless opponent with the helmet, forearm, elbow or shoulder.”

The league noted that a “defenseless opponent” is defined as “one who, because his physical position and focus of concentration, is especially vulnerable to injury.” An example the rule book gives of a defenseless opponent is a receiver whose focus is on catching a pass, the SEC said.

The NCAA is putting increased emphasis — including potential suspensions — on protecting defenseless players this season, as it tries to limit concussions, which are now a widely discussed issue at all levels of football.

“These rules are for the protection of the health and safety of our players on both sides of the ball,” SEC commissioner Mike Slive said in the suspension announcement. “It is imperative that our student-athletes understand the importance of this rule. Our motivation in making these decisions is to protect our student-athletes.”