COLUMBIA - Chad Holbrook was torn between a tired starting pitcher and one of the best bullpens in the SEC when he sent South Carolina pitching coach John Meyers to the mound in the sixth inning.

It was an opportune time to pull junior ace Jordan Montgomery. Holbrook knew it. He thought about it in the dugout.

The junior had struggled in the Gamecocks' conference opener, but Montgomery is the best pitcher on South Carolina's staff. Holbrook calls him the "heart and soul." Hence, his dilemma.

"He was (at his limit), but also I thought his best stuff was in that inning," Holbrook said. "He can go six innings. That's not pushing the envelope. He had one out to get, and he just couldn't get it."

With the bases loaded and a two-run USC lead, Ole Miss leadoff hitter Auston Bousfield ruined South Carolina's conference opener with a grand slam to left field off Montgomery, propelling the No. 21 Rebels to a 6-4 win over the No. 1 Gamecocks before a crowd of 7,859 on Friday night at Carolina Stadium.

The grand slam came on Montgomery's 117th pitch. Holbrook said he's comfortable with his ace up to 120 pitches.

Bousfield's blast gave South Carolina (17-1, 0-1 SEC) its first loss of the season, and dropped the Gamecocks to a losing record in the SEC. Ole Miss (17-2, 1-0 SEC) won its sixth straight game, beating a ranked team for the first time this season.

South Carolina will close its first SEC series with a Saturday doubleheader against Ole Miss. The first game begins at 3 p.m.

"I just left a fastball up, and he hit it," Montgomery said Friday. ". That's just baseball. One pitch. I didn't hit my spot, I missed my spot. He took advantage of it. That's why we love the game, hate the game. Can't really do much about it."

The loss ruined a remarkable night for South Carolina sophomore Max Schrock. A sprained left ankle relegated USC's starting second baseman to the designated hitter spot, and even that role was surprising. On Thursday, USC coach Chad Holbrook said Schrock was "doubtful," maybe 50-50 at best.

Instead, Schrock finished 4-for-5 with two RBIs, including a first-inning solo homer on Ole Miss starter Chris Ellis. Schrock's four hits tied a career high.

"He's a tough nut. He just wants to play," Holbrook said. "He begged his way in there. He took some ground balls before the game today, and it was easy to tell he wasn't going to do that. But I told him (Thursday) DHing was on the table, and I'd consider it.

"He's one of our best hitters, and if he's able to swing we're going to put him in there."

Ellis hadn't allowed a run in four starts this season. He allowed four earned runs on 10 hits in 51/3 innings, his worst outing of the season. He had one strikeout and walked three.

Center fielder Tanner English was 2-for-3 with a double and run scored. First baseman Kyle Martin and right fielder Connor Bright added an RBI.

Montgomery allowed six earned runs in six innings, with six hits, five strikeouts and three walks. After entering Friday with a 1.99 ERA, he exited with it ballooned to 3.45.

Of course, Montgomery's line would've looked much different if he'd never seen his 117th pitch.

"That's baseball. We've seen him get out of those innings, those jams," Holbrook said. ". If I make a mistake by leaving Jordan Montgomery out there, I can live with myself. I can lay my head down at night, because that son of a gun's deserved to try to get those big outs in that situation. He's the heart and soul of our pitching staff. It just didn't go our way."