Mountaineers' junior left-hander Rob Marcello nearly matched Ryan Arrowood's effort, while the ASU bats came alive against LSU's pitching in an 11-1 victory.
Following the loss when the Tigers didn't cross the plate until the bottom of the ninth inning, Tigers' coach Paul Mainieri – just like on Saturday – was baffled by the results, this time even more so.
"I have been in this game a lot of years, and sometimes you have days that are hard to explain," Mainieri said. "It was Murphy's Law for us (Sunday). Everything that could go wrong went wrong. They whipped us every way possible.
"It seemed worse (Sunday) simply because we didn't shut them down and the game became one-sided."
Marcello went 8.1 innings and allowed one run on just three hits and struck out four en route to picking up his second win in as many appearances this season.
"(Sunday) was a little bit easier because we could see that kid a little bit better," said Mason Katz, who batted third in a lineup made entirely of right-handers. "We started to see him a little better in the end, but they had 11 runs, so it was a little too late."
McCune walked the leadoff batter, struck out the next two hitters and then allowed a single up the middle to put runners on the corners.
Tyler Tewell's ground ball narrowly missed the glove of Casey Yocum at second base, which scored Hector Crespo from third base to get Appalachian State on the board first.
The Tigers almost had an immediate answer in the bottom of the frame after Yocum reached on a one-out single to left field, then Katz reached base on a full-count walk and broke up a double-play chance off Raph Rhymes with a hard slide into second, which moved Yocum to third.
Rhymes moved to second on a wild pitch, but a groundout by JaCoby Jones ended the threat.
"I thought we hit some balls pretty hard early in the game," Mainieri said. "It just seemed like when we are on offense the holes seemed small, then when they are up to bat the holes seemed big."
Added Katz: "You sit there and ask why. There are days where everything is going to fall, and then there are days where nothing is going to fall. That's how it was (Sunday). That's how the game of baseball goes."
Unlike Saturday, when Ryan Eades worked a one-run game from the mound, McCune was unable to find his rhythm and stop the bleeding.
"I think the starting pitcher's role is to set the tone of the game," McCune said. "Giving up four runs in three innings is not setting the tone. I take full blame in the start (Sunday).
"I can't just rely on my fastball. I have to come out next game with better stuff."
McCune's day ended after he allowed four runs on seven hits in three innings of work – the shortest outing of his career.
In came Bourgeois, but the runs continued to pile up.
When Brent Bonvillain took over in the sixth inning, LSU trailed 5-0.
"I decided to take Kurt out thinking that maybe we could change the momentum there a bit," Mainieri said. "But they chip away at another one and all the sudden we are in a bigger hole. It just continued and continued.
"It was tough to take."
Kevin Berry, Chris Cotton, Michael Reed and Nick Rumbelow all tried their hand from the mound for LSU, but after keeping the Mountaineers off the board in the fifth and sixth innings, the Appalachian State bats were able to put two runs on the board in each of the final three frames.
"Coach told us coming into this game that this was a very good team and that they deserved a better reputation than they had," McCune said. "It was surprising they put up 11 runs on us, but we knew coming in that they could hit the baseball."
After the weekend started with LSU securing a 4-0 win on Friday night, Mainieri credited the Mountaineers for sticking with their guns and moving forward to capture the series.
"They don't hang their heads," Mainieri said. "They still believed in themselves.
"This is more of a situation where Appalachian State just played great, and they took it to us."
What does that mean for an LSU side that has run into a wall from the plate, scoring just one run in the last 20 innings of baseball?
"We need to do some self-analysis and see where we need to improve," Mainieri said. "And we need to have a big week and try to erase some of these memories."
The Tigers are back in action against Grambling on Tuesday night at Alex Box. First pitch is set for 6:30 p.m.