Molina suffered a left shoulder, neck and upper back strain in the collision, which ended the second inning. Tests run on Molina when he exited the game did not show signs of a concussion, though that can't be entirely ruled out yet.
The play happened with the Pirates leading, 1-0, and Harrison trying to score from second on a two-out single. He arrived at home at the same time Carlos Beltran's relay throw from right field did, and in an attempt to knock out the ball, Harrison knocked down Molina.
Molina held on for the inning's final out but had to be helped off the field by the Cardinals' training staff. Afterward, several St. Louis players -- though none willing to speak on the record -- questioned whether Harrison's hit was clean.
Harrison and Pirates manager Clint Hurdle saw it differently, with Hurdle explaining his view as such:
"Just an old-fashioned baseball play. You never like to see people get hurt -- and I hope he is not hurt. But watching from the dugout and later on tape ... he took the plate away from Josh. Josh had no place else to go. So a baseball play happened."
Molina had not yet seen a replay of the hit by the time reporters approached him after the game.
"Hopefully it's a good play. I have to wait and see," Molina said. "I was concentrating on catching the ball. I never saw him coming. The pain was on my head, but I don't know if [Harrison's arm] was straight to my head or not."
The spark from Harrison's hit, coupled with Westbrook's command problems, propelled the Pirates' offense to a big night.
On the heels of a shaky five-inning start on Thursday, Westbrook endured one of his worst of the year. He lasted five innings again, but exited with the club down seven.
"The fact that I didn't throw the ball very well tonight kind of compounded that whole situation [with Molina]," Westbrook said. "It's something I need to do a better job of, getting back in the game and more consistent."
Westbrook gave up 11 hits and a season-high four walks. Five of those Pittsburgh hits came in the fifth, when the Pirates pulled away with a four-run inning. The inning opened with four straight hits, before Westbrook plunked Harrison to load the bases.
Home-plate umpire Adrian Johnson issued warnings to both benches, a decision that Hurdle contested.
"All I have to say -- and I'll share the rest of my comments with the league office -- is this: A baseball play was made at home plate," Hurdle said. "If they decided to pitch Josh Harrison tight, that's also a baseball play. We didn't have an opportunity to make that baseball play. And if [the umpire] thought the intent was to hit Josh -- throw the pitcher out, and let's go on."
After Hurdle's on-field spat with Johnson, Pirates shortstop Clint Barmes connected for a two-run single.
Four of the Pirates' runs were driven in by Pedro Alvarez, who has been a nuisance to St. Louis this year. With two home runs on Tuesday, Alvarez now has six homers and 20 RBIs in 14 games against the Cardinals. His 469-foot blast off reliever Brandon Dickson in the sixth was the longest home run ever hit by a Pirates player at PNC Park.
Alvarez is batting .389 against the Cardinals this year. His average against everyone else: .225.
"He's hit us well. There's no denying that," Cardinals manager Mike Matheny said. "We respect the fact that he can do what he did tonight. But once again, when we get into counts that are hitters' counts, the odds of that happening go up quite a bit."
For Westbrook, the troubles against the Pirates are hardly anything new. He dropped to 1-4 in five starts against Pittsburgh this year. His career ERA against the organization spiked to 5.28.
"I can't figure it out," Westbrook said. "They just seem like they do a good job of putting good at-bats against me, and it's that much tougher when I'm not pitching very well, which was the case tonight."
While Westbrook labored, Pirates starter James McDonald sailed. Despite his terrible second-half numbers, McDonald continues to find success against the Cards. After holding St. Louis scoreless in six innings on Aug. 17, McDonald pitched seven scoreless on Tuesday.
In comparison, McDonald has allowed 34 earned runs and 47 hits in the other 36 innings he's pitched since the All-Star break.
The Cardinals managed just two hits and a walk off McDonald.
"We had a game plan of making him throw strikes, keeping him in the zone," second baseman Skip Schumaker said. "He did that. His last few starts it looked like he was very erratic, and today it felt like we would wait to take a strike, and it was strike one right away."
With the loss, the Cardinals' lead over the Pirates in the division and Wild Card standings is two games. The clubs are now 7-7 against each other this year. Wednesday's game is the final one to be played between the division foes.