Koger, who began the year as Auburn's No. 1 starter, gave up five runs in an inning of work for the Tigers to drop his record to 0-3. He gave up three hits and walked three Gamecocks as the Tigers fell to 31-21 on the season.
Jacksonville State, which lost to Auburn 12-8 last week, took the victory on Tuesday night despite managing just five hits off of four Auburn pitchers.
"We didn't bring our ‘A' game tonight," Coach John Pawlowski said. "We didn't do the things necessary to win."
Auburn managed just five hits. "Give them credit, they pitched well," said Pawlowski, who noted his Tigers didn't do a good job of adjusting to a diet of off-speed pitches and not-so-fast fastballs after seeing plenty of heat over the weekend in winning an SEC series at Florida.
"Our guys are disappointed and they should be," the coach added.
One of the few bright spots for Auburn was the return to action of pitcher Rocky McCord, who had not been in a game since the LSU series. He threw two innings, struck out three batters and did not give up a hit.
"The mindset was one or two innings to get him back out there to make sure he is good to go," Pawlowski said of his starter vs. the Gamecocks. "I was really encouraged by that."
The coach noted that right-hander's arm had been bothering him, explaining the sophomore's absence from game action. "We have been bringing him along slowly trying to get him back in there," Pawlowski added. "That was a big step for him tonight."
Neither team managed a hit in the opening two innings, but the visitors jumped on top in the third after McCord was replaced by Koger. With two outs in the inning a single by Cal Lambert was followed by a two-run homer over the Green Monster by Michael Bishop to put the visitors up 2-0. That was all the runs the visitors would need.
Koger created more trouble for the Tigers by walking the opening two batters in the fourth inning to set the stage for the Gamecocks to score four more runs on just two hits in an inning finished on the mound by Trey Cochran-Gill.
Auburn didn't get a hit until a Damek Tomscha doubled in the fifth inning. The Tigers' first big scoring opportunity came in the sixth inning when Auburn loaded the bases with two outs, but couldn't push a run home when Jordan Ebert struck out to end the threat.
Ebert got a do-over with the bases loaded in the bottom of the eighth inning with one out and drove home Auburn's only run of the game with a sacrifice fly deep to center field scoring Cullen Wacker. Ryan Tella then struck out to end the threat.
The Tigers will close the regular season with a three-game home series vs. Arkansas. Game times are 6 p.m. on Thursday and Friday with the finale at 1 p.m. Saturday.