Braves left-handed pitching prospect Kolby Allard will make his major-league debut Tuesday against the Marlins.

Allard will become the third 20-year-old to debut with the Braves this season, joining outfielder Ronald Acuna and right-hander Mike Soroka. He’s ranked the Braves’ No. 8 prospect by Baseball America.

“He’s been in the mix a long time,” manager Brian Snitker said. “It’ll be good to get him out there. ... I’ve heard a lot of good things, really, from the last few years.”

Allard already had a locker in the Braves clubhouse Monday. He’ll wear No. 36.

The Braves selected the southern California native in the first round of the 2015 draft. He quickly ascended the ranks, spending his full age 19 season in Double-A Mississippi.

Allard posted a 3.18 ERA with a 129:45 strikeout-to-walk ratio in Double-A. His innings jumped from 87-2/3 in Single-A to 150.

After a taste of big-league spring training, Allard opened the season with Triple-A Gwinnett with Acuna and Soroka. He’s since thrown 109-1/3 innings with a 2.80 ERA.

The Braves scratched Allard from his scheduled Sunday start. His addition will give each starter an extra day off – the Braves have just four off days remaining this season, and will play 31 of the next 32 days.

“Just to kind of stretch everyone out and it worked out good where we’re at,” Snitker said. “I’m excited to see him. He’s had a decent year. ... With this stretch we’re in now, really until the end of the year, we don’t have a lot of off days. We’re playing a lot of baseball. So it’ll be good to get him in there.”

It’s unclear if Allard is being promoted to stay.

Allard is commonly referred to as a high-floor prospect. Some evaluators question his ceiling with a fastball in the high-80s, low-90s. His developing change-up has given him three plus-pitches.