Cincinnati outfielder Tommy Pham was in the original lineup, then removed and traded to Boston for a player to be named or cash.
Miami has lost eight straight home games and 11 of 15 overall.
Greene (4-12) struck out eight and walked none. He had been 0-5 in eight starts since beating Arizona on June 6.
Reiver Sanmartin, Ian Gibaut and Hunter Strickland finished the five-hitter. Strickland allowed pinch-hitter Nick Fortes’ two-out run-scoring single, then retired Jacob Stallings on a flyout for his seventh save in 10 chances.
Three batters reached against Greene, who topped 100 mph with six pitches and averaged 98.6 mph with his fastball. Charles Leblanc singled off the 22-year-old right-hander with one out in the third, and Green hit a pair of batters with pitchers, Jesús Sanchez in the fifth and Stallings in the sixth.
Jesús Luzardo (2-4) gave up two runs and three hits in five innings and struck out five. It was the first big league outing since May 10 for the 24-year-old lefty, who had been sidelined by a left forearm strain.
Almora played his first big league game since July 10 following a stint on the COVID-10 injured list and broke an 0 for 17 slide with a two-run double in the second that landed on the right-field warning track.
Jonathan India’ added a two-out RBI single in the seventh against Steven Okert.
MOVING UP THE LIST
Votto tied Eddie Murray with 1,333 walks for 38th.
Reds: Reinstated Hunter Strickland from the bereavement list. OF Stuart Fairchild and RHP Ryan Hendrix were optioned to Triple-A Louisville.
Reds: C Tyler Stephenson (broken right clavicle) was transferred to the 60-day injured list. ... INF Max Schrock was expected to join the club on its taxi squad for the series in Miami before he fractured his right kneecap in a game Saturday at Louisville.
Reds RHP Graham Ashcraft (4-2, 4.64) will pitch the second game of the series Tuesday while the Marlins will go with LHP Braxton Garrett (2-4, 3.96).