PHOENIX -- Standing on a major league mound for the first time this spring brought out the best in Homer Bailey.
"I tried to treat today like more of regular-season game," said Bailey, who struck out seven. "Being inside a real stadium and the noises and atmosphere helped. Spring training is kind of dead as far as the noise goes. So that kind of helped a bit."
Bailey was coming off a start in which he allowed nine runs -- eight earned -- on nine hits and two walks with five strikeouts in 3 1/3 innings against Seattle.
Against the Diamondbacks, he gave up only a one-out single to Cliff Pennington and a two-out walk to Gerardo Parra, both in the third inning. Bailey retired his final 10 batters and threw 63 of 94 pitches for strikes.
"Some people were worried because he didn't have a good spring, but he was throwing the ball well," Reds manager Dusty Baker said. "Always tell my guys to finish strong, and that's what he did."
Arizona left-hander Wade Miley also worked six innings, allowing four runs and nine hits with two walks. Miley, last season's NL Rookie of the Year runner-up, struck out three.
"I struggled a little bit early but was able to come back," he said. "The ball was coming out fine. Before I was just kind of guiding it in there and it didn't have that late life. I just need to throw it instead of thinking about it, just go out and let it fire."
Bailey singled and scored during Cincinnati's three-run third inning. Joey Votto hit a run-scoring double with two outs, Ryan Ludwick walked and Jay Bruce and Todd Frazier added consecutive RBI singles.
Zack Cozart doubled and scored in the fifth to make it 4-0.
Cincinnati added a run in the eighth and four more in the ninth, two coming on four hits against reliever Heath Bell.
Diamondbacks manager Kirk Gibson said after the game that left-hander Patrick Corbin will be the team's fifth starter. The 23-year-old Corbin made his major league debut April 30 and finished 6-8 with a 4.54 ERA last year in 22 appearances, 17 starts. ... Arizona completed a five-year, $32 million contract with 1B Paul Goldschmidt. The contract runs through the 2018 season with a $14.5 million club option for 2019. ... The Reds will announce their final roster moves on Sunday. ... Miley has given up eight runs and 15 hits over 9 1/3 innings in his last two starts. ... The Diamondbacks optioned OF Tony Campana and LHP Joe Paterson to Triple-A Reno after their game Friday night and reassigned RHP Nelson Figueroa and C Tuffy Gosewich to minor league camp. On Saturday, the Diamondbacks released C Mark Reed, but he'll remain with the team as a bullpen catcher. ... RHP Johnny Cueto opens the regular season for the Reds on Monday against RHP Jered Weaver and the Los Angeles Angels in an interleague game. ... Arizona RHP Ian Kennedy gets the ball Monday night against St. Louis RHP Adam Wainwright. Former Diamondbacks right-hander and 2006 NL Cy Young Award winner Brandon Webb will throw out the ceremonial first pitch.