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Chris Iannetta homered twice and drove in a career-high six runs and Juan Nicasio pitched seven solid innings in his major league debut as the scuffling Colorado Rockies routed the St. Louis Cardinals 15-4 on Saturday night.

The hard-throwing Nicasio (1-0) surrendered just six hits and one unearned run after being recalled from Double-A Tulsa to make a spot start.

Nicasio may have just made a compelling case to stick around a while longer as the Rockies tinker with their rotation in the wake of the season-ending elbow injury to Jorge De La Rosa.

The usually reliable Jaime Garcia (5-1) had a rough outing and the Rockies took full advantage to break out of their offensive funk by setting season highs for runs and hits (18). They also ended a four-game slide in which they scored a total of nine times.

Garcia surrendered 12 runs — 11 earned — and 11 hits, both career highs. He was eventually pulled with one out in the fourth in his shortest outing of the season.

The crafty lefty entered with a minuscule 1.93 ERA, but saw it balloon to 3.28 by the time his night was finished. Garcia surrendered six runs and threw 49 pitches in the first inning alone.

Iannetta had his first multihomer game, both shots landing deep in the left-field seats. He also had a two-run single in the first.

Ryan Spilborghs had three hits and drove in four runs, while Carlos Gonzalez, Troy Tulowitzki and Eric Young Jr. also had RBI singles for the Rockies. Alfredo Amezaga had a sacrifice fly.

Nicasio's blazing fastball was on display early as he hit 95 mph on his first pitch.

His nerves were apparent as well, walking Albert Pujols on four straight pitches. Not the first pitcher to do that, though.

The 24-year-old settled into a groove against the best hitting squad in the majors. He didn't allow a run until the fifth when Tony Cruz doubled and scored on Ryan Theriot's groundout.

By that time, the Rockies were already comfortably ahead 12-0.

Soon after, Cardinals manager Tony La Russa began pulling his players to give them some rest. Yadier Molina came out, along with Lance Berkman and Pujols.

This was the second time Nicasio has stymied a Cardinals squad this season. Earlier this month, he struck out 10 against the Springfield Cardinals, the Double-A affiliate for St. Louis.

While Nicasio cruised along, Garcia couldn't find his customary rhythm.

The Rockies roughed up Garcia right off the bat, scoring six times in the opening frame.

It was an unexpected start, considering Garcia had allowed just one first-inning run over his previous 10 starts.

Garcia gave up four hits and a walk before he recorded his first out, with Gonzalez and Tulowitzki both delivering RBI singles.

He was later called for licking his fingers on the mound before a 1-2 pitch to Spilborghs, resulting in a ball and eventually leading to a run-producing walk.

Iannetta also added a two-run single in the inning, before Garcia struck out Nicasio and got Dexter Fowler to hit into a fielder's choice to halt the rally.

The six runs tied for the most the Rockies have scored in an inning this season. They also had six on April 14 in the sixth inning of game No. 2 during a doubleheader against the New York Mets.

Garcia also was involved in a bizarre play in the fourth. With Gonzalez hung up in a rundown between home and third, Garcia charged at him, threw the ball to third and then didn't get out of the way as Gonzalez ran into him. Gonzalez was awarded home because of obstruction.

Notes: To make room for Nicasio on the roster, the Rockies optioned reliever Bruce Billings to Triple-A Colorado Springs. ... Rockies OF Seth Smith (groin) took swings in the cage before the game. ... Cardinals OF Matt Holliday was not in the lineup for a fifth straight game due to left quadriceps tightness. He entered as a pinch hitter in the eighth and flew out.