This wasn’t supposed to happen to South Carolina.

But it did.

It was a slap-in-the-face reality check.

All was not right in Gamecocksville.

The Gamecocks discovered they have to find a different way to win a football game other than the ones they did in the previous 4 weeks. You can’t always just show up and expect to go through the motions, even though all signs were pointing to it.

The script on Homecoming Day called for another fast start for the newly anointed 25th-best team in the country — according to the AP poll — against Missouri at Williams-Brice Stadium. And then let South Carolina’s running game and controlled passing game take control.

The Gamecocks would walk off early Saturday evening with a robust crowd of 77,000-plus crazed applauding their 5th straight victory, a bowl game literally clinched, and some momentum gained toward a game at Vanderbilt next Saturday night to kick their streak into another gear.

Instead, the chorus of boos at game’s end told the story. Rightfully so, the Gamecocks weren’t the same team they were the past 4 weeks. They went from running on cruise control to running in 1st gear.

South Carolina (5-3 overall, 2-3 SEC) got pulled back down to earth from its ascent in a 23-10 loss to Missouri (4-4, 2-3). The Gamecocks had a clunker at a time when they could least afford one. They were out of sync in the 1st half and never recovered.

Offensive coordinator Marcus Satterfield has remained under fire during the Gamecocks’ recent run of success, and his offense sputtered against Missouri. The pitchforks and torches will be out again this week, and Satterfield will need to find some creativity next week.

Still, this comes down to executing.

On a perfect autumn afternoon for football, South Carolina was reminded of one of the game’s and life’s most recognizable idioms — don’t take anything for granted.

The hype of the 4-game winning streak coupled with all 3 phases of the Gamecocks’ game humming like a new engine lifted their confidence level to a high that hasn’t been present in recent years. Throw in a Top 25 spot for the 1st time in 4 years, and the Gamecocks were strutting their stuff.

But it was apparent that the Gamecocks overlooked the Tigers, who had lost 3 of their previous 4 games and only had 1 conference victory coming in.

The Gamecocks were confident that MarShawn Lloyd would have another big game after he had accumulated 451 yards and scored 7 touchdowns over his past 4 games. Quarterback Spencer Rattler would have to just do enough as a game manager and have another efficient but not overly impressive game.

South Carolina’s defense would have another aggressive outing and snare a turnover or 2. The special teams’ unit would produce another gem.

Unfortunately, none of it happened.

And the Gamecocks lost the Mayor’s Cup trophy for the 4th year in a row.

They watched an underestimated Missouri team take control of the game early with 2 impressive and lengthy scoring drives — one a 15-play, 96-yard march and another a 10-play, 84-yard promenade. The Tigers would add another grinding drive of 10 plays and 75 yards.

Suddenly, Missouri was ahead 17-0 with 4:59 left in the 1st half. Rattler would generate some life when he scored on a 7-yard scamper with just 47 seconds left in the half. But the South Carolina offense was on life support for most of the game, as it produced only 186 yards of total offense.

After halftime, when the Gamecocks were thriving most in their past 4 games, they netted only 82 yards.

Lloyd’s 30 yards rushing was his lowest output since he had 22 in Week 3 against Georgia. Rattler had a sub-200-yard game — 20-for-30 passing, 171 yards, 1 interception — for the 3rd time in a row, but this time it wasn’t enough. It also didn’t help that Rattler was sacked 4 times.

The attacking defense that had been forcing turnovers and closing gaps was torched for 363 yards, including 143 on the ground. Missouri quarterback Brady Cook had the South Carolina defense’s number throughout the game. The Gamecocks’ secondary didn’t have any answers for wide receiver Dominic Lovett, who put on a clinic with 10 catches for 148 yards.

And the special teams’ unit couldn’t pull anything out of its bag of tricks.

It was an afternoon in which South Carolina watched Missouri show it how the Gamecocks won a football game in the past 4 weeks. Run the ball, have your quarterback be a combination of an effective game manager and playmaker, and play an aggressive and shutdown defense.

Missouri converted 8 of 16 third downs and scored on 5 of 11 possessions — not glowing stats for the South Carolina defense.

Gamecocks head coach Shane Beamer was confident his team wouldn’t submit to the ‘C’ word.

“We didn’t do a good job in creating turnovers,” Beamer said in his postgame press conference. “We had four wins in a row, and we had a big win last week. We were ranked for the first time in … forever.

“It’s easy to say South Carolina will get complacent, and not play with the same energy and physicality that they had been. We were on guard for that all week. We had a great week of practice, great energy and great physicality.

“We looked like a team that was on our heels in the first quarter and waiting for something to happen. We assumed everything would be OK. But in this conference, every week is a grind.”

Ah, don’t assume. Play the old word game with the letters and you’ll find out what happens when you do.

South Carolina did. For the Gamecocks, it could prove costly. Many believed Missouri would be win No. 6.

Now, with only 1 home game left and facing 2 ranked teams on the road in the final 4 weeks, the Gamecocks will have to learn their lesson.