The Mariners dipped to 66-83 -- including a 4-10 mark in September -- and now head to Detroit for a four-game set with the American League Central-leading Tigers.
Ramirez, who missed the first three months of the season with a sore elbow, picked up his first road loss of the year in falling to 5-2 with a 4.98 ERA in 12 games.
The 23-year-old lasted just four innings while surrendering five runs on eight hits and throwing 80 pitches, only 45 of which were strikes. Ramirez normally relies on his command, but he hit two batters in a four-run fourth and wasn't as crisp as he'd been while posting a 2.27 ERA over his previous five starts.
"He just fell out of his delivery, that was the big thing we saw," said manager Eric Wedge. "And with that, he really lost command of the baseball. When he did throw it over, it really wasn't pitches that were executed. It was more fat and on the plate. So it happened quick."
Ramirez didn't walk a batter, but his inability to throw quality strikes -- not to mention the two hit batters -- led to his rough day.
"Those situations aren't usual for me," he said. "I don't know. The ball was running too much and I hadn't felt that happen before. It's part of the game, they took advantage of every mistake I made and I was behind in the count a lot. Now I just have to think about it and go for the next start. This one is already done. I already lost."
Ramirez gave up a leadoff home run to Yadier Molina in the second inning, a 402-foot shot into the Mariners' bullpen in left field on a 2-2 curveball.
Seattle tied it back up in the fourth when rookie center fielder Abraham Almonte doubled and scored on Franklin Gutierrez's single up the middle.
But the Cardinals broke things open in the bottom of that inning with four runs on five hits and two hit batters. A bases-loaded single by Daniel Descalso pushed across the first run, then Matt Carpenter looped a two-run single just over the glove of leaping shortstop Carlos Triunfel for a 4-1 lead.
Matt Holliday plated another run with a bases-loaded single with a hard shot off Ramirez's glove before the Nicaraguan right-hander got out of the inning by retiring Carlos Beltran for the second time in the frame.
The Mariners managed an unearned run in the fifth when pinch hitter Endy Chavez -- batting for Ramirez -- reached on an error and eventually scored on a sacrifice fly by Almonte.
But Seattle's bullpen couldn't stem the tide as Carter Capps replaced Ramirez and promptly gave up three hits and three runs -- including a two-run bomb by first baseman Matt Adams -- without recording an out as the Cardinals put up another four-spot in the fifth to make it 9-2 and never looked back.
Capps has pitched better at times since being recalled from Triple-A Tacoma, but the hard-throwing 23-year-old got hit hard in a hurry on a single by Molina, the two-run homer by Adams and a double by David Freese.
"Today he kind of reverted back," said Wedge. "He threw six or seven pitches and they were all fastballs and most of them up. I don't care how hard you throw, you're not going to get away with that here."
The Cardinals wound up with 11 of their 19 hits on the day against four Mariners relievers as Capps, Bobby LaFromboise and Chance Ruffin allowed seven runs before Lucas Luetge pitched a 1-2-3 eighth.
"The bullpen really struggled today, too," said Wedge. "It's tough. You've got a couple guys you feel like you can count on that have been doing it for awhile, but other than that, you're just trying to figure out where everybody is down there. Hopefully they can make some progress. They're getting opportunities and that's the most important thing."
Gutierrez had two singles for Seattle and Almonte extended his hitting streak to five games with his double, but the Mariners totaled just five hits. Molina had four himself for St. Louis in a 4-for-5 day with three runs scored as the Cardinals racked up their second-highest hit total of the season, behind only their 21 hits that came on July 14.
Cardinals right-hander Shelby Miller, a 22-year-old rookie, improved to 14-9 with the win.
"You know, it's not hard when your offense goes out there and puts up a lot of runs like that," said Miller. "They don't have a bad lineup over there at all. Seattle has obviously got some great hitters and some guys that have power. For our offense to go out there and put up a lot of runs like that is huge for us."