MIAMI (AP) -- As soon as Patrick Corbin threw his first major-league pitch Monday, his nerves began to settle. The final pitch of the first inning made him feel even better.
Corbin escaped a bases-loaded jam in the opening inning and went 5 2-3 innings to win his major league debut by helping the Arizona Diamondbacks beat the slumping Miami Marlins 9-5.
"He did a great job for a young kid to come in that situation," manager Kirk Gibson said. "He was very excited. The ball was elevated a little more than he wanted to early, but he kept his composure and made his pitches."
The 22-year-old Corbin, who was called up from Double-A Mobile, struck out six and allowed three runs. With 15 friends and relatives in attendance, mostly from his native New York, the left-hander said he was a bit nervous at the start but calmed down quickly.
"After the first pitch, I was ready to go and get after it," he said. "It felt great being out there."
Corbin loaded the bases with one out in the first, but Omar Infante bounced into a 1-2-3 double play.
"Definitely after that I took a big breath when I got in the dugout," Corbin said.
One day after jumping ahead 8-0, the Diamondbacks were up 7-0 by the fifth inning. Cody Ransom and Justin Upton hit two-run homers, and Willie Bloomquist had a two-run double.
The Marlins lost for the eighth time in nine games and had fans booing for the second consecutive day.
"Can you blame them?" manager Ozzie Guillen said. "I was booing, too."
Miami, expected to contend for a division title after an offseason spending spree, is 8-14 and last in the NL East as it begins a nine-game trip. Guillen criticized his players' failure to change their approach at the plate or on the mound.
"If you cannot make an adjustment, I will make it for you," he said. "I'm going to make a very drastic change. I don't know which one yet, but I'm going to make an adjustment. I'm pretty good at that. That's my job."
Mark Buehrle (1-4) endured his worst outing this season. Facing Arizona for the first time in his 370th career start, the left-hander lasted only five innings and allowed seven runs - four earned - and eight hits.
"I guess it could get worse," Buehrle said. "We won eight games this month. We could have won none. We've got to keep going at it."
Miami committed three errors, including one on a misplayed bunt that led to a five-run inning, and struggling closer Heath Bell gave up two runs in a non-save situation in the ninth.
After the Marlins threatened in the first, they didn't manage another hit off Corbin until the fifth.
"He kept it simple," 40-year-old catcher Henry Blanco said of his young teammate. "He didn't try to do too much, just tried to get ahead of the hitter. I think that's all you can ask for in your first start."
Corbin left in the sixth after he allowed a single by John Buck and a homer by pinch-hitter Donnie Murphy . Even so, Arizona's starters have an ERA of 1.32 over the past four games.
Miami's Austin Kearns hit a two-run homer in the seventh. J.J. Putz pitched a scoreless ninth, reducing his ERA to 4.70.
Arizona's A.J. Pollock had a sacrifice fly and two hits to hike his average to .136 for the Diamondbacks, who climbed above .500 by winning three of four games in the series.
"Overall I think we have been playing great," Gibson said. "Guys are loose and enthusiastic to play the game."
Thanks to the retractable roof on the Marlins' new ballpark, a rainout may have been averted for a second day in a row. Announced attendance was 31,008, and the afternoon crowd included 12,000 schoolchildren who generated a high-pitched din throughout the game.
NOTES: Arizona LF Jason Kubel was scratched from the lineup shortly before the game because of illness. ... Before the game, the Diamondbacks optioned RHP Joe Martinez to Triple-A Reno. INF Geoff Blum (strained left oblique) was transferred to the 60-day disabled list. ... Marlins RHP Ricky Nolasco , scheduled to start Tuesday at San Francisco, is 3-0 in three starts there with an ERA of 0.76. ... LHP Dan Jennings was in Triple-A and planning to attend a wedding shower with his fiancee this week in Iowa, but those plans were put on hold when he was called up to the majors for the first time. He joined the Marlins before the game and pitched a hitless sixth. ... Marlins attendance topped 30,000 for the eighth time in 11 home games.