With closer Kyle Farnsworth (right elbow tenderness) ailing, manager Joe Maddon and general manager Andrew Friedman chose to bring up the 22-year-old Moore, arguably the top pitcher in the Minor Leagues.
To make room on the 40-man roster for the young lefty, the Rays designated Rob Delaney for assignment.
In 155 innings pitched for Double-A Montgomery and Triple-A Durham, Moore was 12-3 with a 1.92 ERA and his 210 strikeouts ranked second among all Minor Leaguers.
"With Kyle being hurt right now, I thought we needed some help in the bullpen," Maddon said, adding he does not expect Farnsworth to pitch on Monday. "Why not bring your best arm to be that guy? It worked for us in the past very successfully."
Maddon is referring to the 2008 season when David Price joined the big league club over the final few weeks of the season and became a valuable contributor to a World Series run.
Now a stalwart in the Rays starting rotation, Price worked out primarily out of the bullpen during that first taste of the big leagues. Maddon expects a similar role for Moore, and will look to use him at the top innings to help mimic a starter's traditional warm-up. Ultimately Maddon said he's not going to force the young hurler into action just for the sake of it. There are both short and long term implications at stake.
"I want to be very careful with him. He's a huge part of our future," Maddon said. "It's a balancing act that you have to perform. Trying to win the game and still maintain the integrity of this fella's arm for years to come."
With his Minor League season over, Moore was planning a cross-country drive from Durham to his native New Mexico on Tuesday, when suddenly he had a new destination.
"I was getting my oil changed [Sunday], about to drive 30 hours across the country," said the fresh-faced Moore, who instead hopped on a one-hour flight to Baltimore. "And here I am on Monday in Baltimore getting ready to suit up for my first big league game in Baltimore. It's exciting times."