DENVER (AP) -- The music was muffled and the mood melancholy in the Colorado clubhouse even after one of the Rockies' biggest wins of the young season.
Carlos Gonzalez homered twice and the Rockies became the first team to decipher Josh Collmenter 's tomahawk-throwing style, rallying past Arizona 12-4 on Tuesday, but they lost pitcher Jorge De La Rosa in the opener of the day-night doubleheader to a torn elbow ligament.
Then they lost the nightcap 5-2 when Joe Saunders (1-5) snapped a personal six-game losing streak and Kelly Johnson hit a solo homer and had one of three RBI doubles off Jhoulys Chacin (5-3) in the sixth inning.
In between games, the Rockies learned they'd be without their best pitcher the rest of the season.
"It's devastating," Jason Giambi said. "He was having a phenomenal year for us, too. I feel terrible for the kid. He was really putting it together. That happens in baseball and now we've got to pull together."
The team said an MRI showed a complete tear of the ulnar collateral ligament in De La Rosa's left elbow, and manager Jim Tracy said he'll undergo Tommy John -style tendon replacement surgery. That will sideline the hard-throwing left-hander for a year.
De La Rosa was the Rockies' top pitcher so far with a 5-2 record and a 3.51 ERA. He was coming off his first career complete game when he got hurt.
With Ubaldo Jimenez still searching for his first win, De La Rosa had been the Rockies' rock.
"He was a big part of our team," said Greg Reynolds , who won the opener in relief. "There's not too many guys that have stuff like Jorge."
"Guys are going to get hurt, key guys," Todd Helton said. "You've got to find a way to overcome it. It's something we have no choice but to overcome."
During the opener, a 27-year-old man was critically injured when he fell from a stairwell leading to the center field seats at Coors Field. Police spokesman Sonny Jackson said the man was hospitalized in critical condition following a fall of approximately 20 feet onto concrete.
Reynolds (2-0) threw 3 2-3 effective innings in the opener, allowing one run and three hits. He was recently called up and set to start Saturday, but was pressed into duty when De La Rosa had to leave the game, which was a makeup from an April 3 snowout.
Collmenter (3-1), the Arizona rookie with the unusual straight overhand delivery, blanked Colorado for three innings to run his scoreless streak to 24 before he gave up solo homers to Gonzalez and Seth Smith in the fourth.
Collmenter allowed five runs, just two earned, and five hits in 4 1-3 innings. He walked two and struck out one.
"I missed a few spots, location was off today," Collmenter said. "It wasn't going out there and putting it wherever you wanted, I had to fight it today."
The 25-year-old righty, who says he learned to throw that way playing with tomahawks as a kid, left the game in the fifth with the bases loaded following an error on first baseman Xavier Nady , a single and a walk. Reliever Kam Mickolio walked Tulowitzki before allowing Helton's sacrifice fly and Smith's RBI double that gave Colorado a 5-3 lead.
Coming into the game, Collmenter had allowed two runs in 26 innings, with 15 strikeouts and one walk since being called up from Triple-A Reno.
De La Rosa left the game with a 1-and-1 count on Chris Young and two on in the third.
"As the at-bat progressed it became more evident that there was something wrong. I thought maybe it was a blister or nail issue," catcher Chris Iannetta said. "I went out and talked to him and he didn't really sound good. I saw his demeanor while he was receiving signs and said enough's enough."
Tracy said he watched De La Rosa grimace on a practice pitch to the plate and knew he was done.
The D-Backs bounced back in the nightcap behind Saunders, who pitched a season-best eight innings, allowing two earned runs on six hits over eight innings.
Saunders said he thought for a second that he wouldn't even reach the fourth inning after his collision with Dexter Fowler at the plate for the final out of the third inning.
"He got me good. I caught the ball and he hit me at the same time," Saunders said. "I was focusing on trying to not let him get much of the plate. It's kind of a blur. I remember flipping over and I remember my head smoking the ground. I just laid there because my head was a little numb. I shook it off and had to go back out."
Saunders said he didn't think he had a concussion: "I hope not. It was a little cloudy at the plate, but I just tried to focus the best I could and keep pumping strikes," he said.
Tracy was ejected after arguing with home plate umpire Mark Wegner, who ruled that catcher Miguel Montero 's throw to Saunders, who was covering home after a pitch got away, nabbed Fowler.
The D-Backs took a 1-0 lead on Johnson's sixth homer in the first inning of the nightcap. Johnson scored on Nady's fielder's choice groundball in the fourth after Giambi's solo homer in the second, and Arizona got run-scoring doubles from Johnson, Stephen Drew and Montero in the sixth to make it 5-1.
J.J. Putz pitched the ninth for his 13th save in as many chances.
NOTES: Giambi was plunked in the right elbow by Saunders in the fourth but didn't come out until the eighth after his elbow started to swell. ... D-Backs RHP Juan Gutierrez left the opener with a sore right shoulder after facing just two hitters in the sixth. He's heading back to Arizona to get checked out by a doctor Wednesday.
Arnie Stapleton can be reached at http://twitter.com/arniestapleton