"My first reaction was, 'Wow,'" Flores said through an interpreter. "I ran out there and tried to warm up like I usually warm up when I was down in the Minor Leagues. I was able to do my warmups like I usually do, and I was able to focus and do my thing."
Flores, who wasn't up throwing before Morris was injured, entered with two outs in the sixth and tossed the final 2 1/3 innings, not allowing a run while yielding just three hits and one walk on 35 pitches.
The Rockies banged out two singles off Flores in the seventh, but the Marlins' No. 11 prospect, according to MLB.com, induced a key 4-6-3 double play to escape unscathed. He successfully worked around a one-out walk in the eighth as well.
"My first experience in the big leagues was exciting, and I just went out there and tried to do the same thing I was doing down in the Minor Leagues," Flores said. "And fortunate for me, I was able to have a good outing my first time out."
Originally signed by San Francisco out of the Dominican Republic, Flores was Miami's primary return when it traded Casey McGehee to the Giants last offseason. Flores spent the first part of 2015 with Double-A Jacksonville -- he went 3-3 with a 2.06 ERA in nine starts -- before being called up on Tuesday.
"It's good to see Kendry get an opportunity to come in and pitch very well here in a tough place to pitch," Marlins manager Dan Jennings said. "He utilized some nice breaking pitches and kept his fastball down.
"He really has two months above Double-A, and I think that's a testament to this kid and his future."
Dargan Southard is an associate reporter for MLB.com.