In between, the 25-year-old made his Reds debut.
Gosling, who was 1-0 with a 1.64 ERA in two starts for Louisville, was available to back up in case something happened to Reds starter Aaron Harang before or early in the game. Swing man Matt Belisle was needed the previous night and wasn't available.
"We needed somebody with some length today," Reds manager Jerry Narron said. "You don't expect a starter to go down in the bullpen warming up, but you have to be prepared for it, possibly."
Harang lasted just four innings in Cincinnati's 9-8 win over Florida, so Gosling was summoned for the top of the fifth. He was charged with two earned runs and one hit. Gosling also walked a batter and hit Mike Jacobs in the head with a pitch. Jacobs was down for a moment, but he was not injured.
Before the Reds acquired Bronson Arroyo in Spring Training, Gosling was considered a candidate for the big-league rotation. But after two impressive outings, everything seemed to fall apart for him. He allowed 12 earned runs on 11 hits while completing just two-thirds of an inning over two games.
Since camp, Gosling believed he fixed some bad habits mechanically and toughened up mentally.
"I'm throwing the ball much better," he said. "I got my mechanics straightened out, which helped my confidence. I'm pitching aggressively. My first couple of starts in Triple-A went well. I'll try to keep that going, the aggressive mentality when I pitch, whether it's here or there."
Burns pitched in three of the last four games, and he often struggled to get outs in his seven appearances this season. The right-hander was 0-0 with a 7.56 ERA in 8 1/3 innings, and he allowed all four of his inherited runners to score.
"I'm sure he would have liked to have pitched better," Narron said. "Here's hoping he goes down there and when we need someone, they say 'Mike Burns is pitching great.'"
Shackelford probably would have been called up directly had he not pitched the previous two games for Louisville. The lefty has been the Bats' best reliever, going 1-0 with a 1.29 ERA in seven games. He was 1-0 with a 2.43 ERA in 37 games last season with Cincinnati.
"Shack did a good job for us a year ago," Narron said. "He's a very good guy to match up against left-handed hitters, and we're glad to have him back."
Shackelford was cut near the end of Spring Training, partly because the Reds already had two lefty relievers in Kent Mercker and Chris Hammond. But the 29-year-old also had difficulty throwing strikes, especially to right-handed hitters. Shackelford issued seven walks in 12 innings this spring.
"That's one of the things I didn't do well in Spring Training," Shackelford said. "You can't just go out there and face lefties every day. Situations might call for otherwise.
"I'm just happy I got a chance to come up here as quick as I did, and I hope I can do the job whenever I get called on."
With challenging lefty Dontrelle Willis starting Wednesday's game for Florida, Narron opted to use a mostly right-handed lineup. But he decided to give shortstop Felipe Lopez his first rest, starting Rich Aurilia in his place.
That meant lefty-hitting Scott Hatteberg was starting at first base. Hatteberg had never faced Willis before.
"I didn't tell Hattie last night before he left," Narron said. "He might be shocked when he walks in the door, I don't know."
Lopez entered the game as a pinch-hitter in the eighth inning and had an RBI infield single to second base.
In an added quandary for the Cincinnati bullpen, Hammond was unavailable Wednesday because he was sick with the flu. He came in to be looked at by the trainers, and he was sent home. Not expected to be on the team charter flight after the game, Hammond will meet the team in Milwaukee.
In his first start for Louisville, veteran lefty Darrell May allowed two runs and five hits over 5 1/3 innings, including four scoreless frames to begin the game. May was signed by Cincinnati after he was cut this spring from Twins camp.
The Bats beat Syracuse, 4-3, in 11 innings on Andy Abad's RBI double. Shackelford got the win.
The Reds will commence a seven-game road trip with the first of four games at Milwaukee on Thursday at 8:05 p.m. ET. Dave Williams will start for Cincinnati against the Brewers' Tomo Ohka.