Freese and Matt Holliday each had four RBI and Allen Craig had three hits and three RBI. The Cardinals shrugged aside a 4-0, fourth-inning deficit and sent Houston to its seventh straight loss.
"This team, they get the blood in the water and they can pile them on," Cardinals manager Mike Matheny said.
The Astros are 0-4 while getting outscored 32-8 since interim manager Tony DeFrancesco replaced Brad Mills as leader of the stripped-down roster. Houston has won just seven of its last 50 overall.
"We got 11 hits and some of the guys got some big days, so there is some life," DeFrancesco said. "Unfortunately, once the game gets out of hand it's tough for our guys to continue to bounce back after they've been getting beat on for a while."
Ben Francisco had three hits for the Astros, who were swept for the third time this month and 12th overall.
Westbrook (13-9) won for the fourth time in five starts despite struggles with control two days after getting a new contract for next season with a mutual option for 2014.
Westbrook surrendered five runs on seven hits, two walks and two hit batters in five innings, ending a string of 13 consecutive starts of at least six innings.
Astros rookie lefty Dallas Keuchel (1-6) retired 11 of the first 12 batters, but six of his last seven reached base, one on an error. He earned his first career RBI on a sacrifice fly in the second, but was charged with five earned runs in four-plus innings.
"I felt good today, thought it was going to be another quality start," Keuchel said. "That fifth inning kind of unraveled things."
The Cardinals wrapedp up a 6-3 homestand with a string of contenders awaiting. St. Louis starts a 10-game trip Friday night with three games at NL Central-leading Cincinnati, followed by three at wild card-contending Pittsburgh and four at NL East-leading Washington.
"A very big road trip, there's no doubt about that," Matheny said. "We need to string them together, that's all there is to it."
In another game: *
At New York, Collin McHugh pitched two-hit ball over seven scoreless innings for the Mets in his major league debut, but the Colorado Rockies completed their second straight four-game sweep with a 1-0 victory as Jordany Valdespin misplayed Tyler Colvin's leadoff drive in the eighth into a game-changing triple. McHugh, a 25-year-old righthander, pitched masterfully with nine strikeouts and one walk. But after he left, the Rockies broke through quickly off Bobby Parnell (2-3).
The San Francisco Giants placed outfielder Justin Christian on the 15-day disabled list with a sprained left wrist. All-Star catcher Buster Posey also was out of the lineup for the second straight game because of tightness in his right hamstring.