ST. LOUIS (AP) -- Ian Kennedy has never had a worse day in his major league career.
The Diamondbacks starter set career worsts by allowing 10 runs and 13 hits, including eight in the fourth inning. He even misplayed a double-play opportunity that could have changed everything in a 12-8 loss to the Cardinals on Thursday night.
"It's really going to motivate me to work harder into this next start," Kennedy said. "I hate this feeling. Make sure I don't have this feeling again."
Shelby Miller hit his first career home run and pitched six sharp innings to lead the Cardinals. Miller (7-3) allowed two runs and six hits while striking out nine and walking none.
Arizona scored three times in the ninth, but Edward Mujica came on and got two outs for his 18th save in 18 chances.
Matt Adams and Daniel Descalso homered in an eight-run fourth inning off Kennedy. Matt Holliday and Matt Carpenter also connected for St. Louis.
Kennedy (3-4) nearly escaped the fourth with giving up just one run, but his throw to second on Yadier Molina's comebacker pulled shortstop Didi Gregorius wide of the base. What could have been an inning-ending double play instead led to Adams' three-run homer and Descalso's two-run shot.
"I think we've made that play and we expect to make that play," manager Kirk Gibson said. "It didn't happen today, and it cost us."
Kennedy endured the entire inning and threw 50 pitches. He had 99 total, only 60 for strikes.
He said typically he'll ask his middle infielders which one will cover the bag in a situation like that before he makes a pitch. He failed to do so on this occasion, and when he saw second baseman Cliff Pennington break toward the bag, his instinct was to throw it to him until Gregorius took charge.
But Kennedy double clutched and threw wide.
"That whole sequence, it was perfect," he said. "I was trying to get a double play in that situation. It would have been a lot different if I was able to turn. That's just my fault. I should have known who covered the bag just before that pitch."
The Cardinals hit five homers in a game for the first time since last July 27. The last time they did it at home was June 24, 2005, at the former Busch Stadium.
David Freese extended his career-best hitting streak to 16 games for St. Louis. Descalso scored twice in the big fourth and finished with three hits, including a double.
The first five batters in the Cardinals' starting lineup all got two hits, as did Miller.
Manager Mike Matheny liked what he saw from Miller at the plate, though he hopes the pitcher doesn't let it change his approach.
"You'll take any runs you can get, but we hope he doesn't go up there trying to do that every time," Matheny said.
The Cardinals greeted D-backs reliever Matt Reynolds with back-to-back home runs from Miller and Carpenter to open the fifth and stretch their lead to 12-2.
Arizona scored twice in the first on an RBI groundout by Paul Goldschmidt and a single by Miguel Montero.
Gerardo Parra had three hits, including an RBI single in a three-run seventh. The Diamondbacks scored three more in the ninth when rookie Keith Butler gave up a hit to Pennington and a double to Wil Nieves before walking three consecutive batters.
By then, the D-backs had removed starters Paul Goldschmidt, Miguel Montero and Martin Prado.
"They didn't quit, no doubt about it," Gibson said. "We put a lot of new guys in there and gave a lot of guys a rest, and they pushed to the end. It was a tough game to play in and they did a good job."
NOTES: The Cardinals have gone 9-0-3 in their past 12 series. ... Goldschmidt has an RBI in six consecutive games. ... Carpenter extended his career-best hitting streak to 15 games. Allen Craig has a 10-game streak. ... Miller was 2 for 25 at the plate entering the game. He singled in the second for his first hit of the season. ... Cardinals LHP Kevin Siegrist came in the seventh to make his major league debut after being recalled from Triple-A Louisville earlier Thursday. He struck out four in 1 2/3 innings, allowing one hit.
