ST. LOUIS -- Aledmys Diaz lived three houses down from Jose Fernandez growing up in Cuba, so the Sunday morning news that the Miami Marlins pitcher died in a boating accident hit really hard.

"It's tough," Diaz said Tuesday night with perhaps two dozen media members around his locker. "I'm looking at life differently right now."

Armed with a heavy heart and a changed perspective, Diaz honored his close friend and fellow National League All-Star with a swing that also helped the St. Louis Cardinals win a game they needed desperately.

Belting an emotional grand slam in the bottom of the fourth inning, Diaz gave St. Louis the lead for good in a 12-5 win over the Cincinnati Reds at Busch Stadium.

His 17th homer of the year came on a 2-1 pitch from Robert Stephenson, flying 408 feet and just clearing the fence in deep left-center. The stoic Diaz rounded the bases with gradually moistening eyes, accepting hugs from Yadier Molina at the plate and several teammates in the dugout before taking a curtain call from the crowd of 34,286.

"I felt some serious goosebumps," winning pitcher Adam Wainwright said. "I almost got choked up. I know he was."

Cardinals manager Mike Matheny said, "It was one of those special moments. Watching him cross home plate and then seeing his reaction crossing the guys in the dugout really hit me. I can't understand the load he's carrying.

"It's a tough thing for anyone to deal with. His mind looked like it was somewhere else, but in a good place."

Diaz missed the Cardinals' games Sunday and Monday to travel to Miami to be with Fernandez's family.

Much like Dee Gordon's stunning leadoff homer Monday night that lifted Miami to a win over the New York Mets and opened up tear ducts everywhere, Diaz's homer was a feel-good moment for almost everyone.

Even Stephenson, the rookie pitcher who saw a 2-1 lead turn a 5-2 deficit and, ultimately, a loss because of Diaz's swing, viewed the bigger picture.

"I thought that was unfortunate timing for me, but really a special moment for him," Stephenson said.

From that moment, St. Louis (82-75) took off. The Cardinals battered Cincinnati (66-91) for five homers, including a three-run blast by Jhonny Peralta in the fifth, plus a two-run shot by pinch hitter Matt Adams in the sixth and a solo bomb by Randal Grichuk two batters later.

The result kept the Cardinals within striking distance of both National League wild-card spots. They trail the New York Mets (84-74) by 1 1/2 games for the first slot and the San Francisco Giants (83-74) by one game for the second position.

Wainwright (13-9) gave up 10 hits and five runs over 5 2/3 innings, issuing two walks and fanning six.

Stephenson (2-3), who didn't allow a hit until Matt Carpenter ripped his 20th homer with two outs in the third, permitted five hits and five runs in four innings with a walk and four strikeouts.

Joey Votto whacked his 28th homer and went 3-for-5 with two RBI for the Reds, while Scott Schebler lined a two-run homer in the sixth.

All of that paled in comparison to one swing of the bat by Diaz, who homered off Fernandez on July 28 in the only regular-season matchup between the two. Fernandez promised to fan Diaz three times when the friends met next year.

For reasons no one ever wanted to happen, that rematch won't take place. However, that doesn't mean Fernandez won't live in Diaz's soul every time he takes the field.

"Every time going forward when I put on a uniform, I'll think about him," Diaz said. "He was living the American dream. He enjoyed performing and competing. He had made it. It's tough, but you have to be a professional first of all.

"I know his family has been through a lot the last couple of days. I hope this helps."

NOTES: St. Louis LF Matt Holliday (right thumb fracture) appears doubtful to return this year. Swelling hasn't abated in the thumb, preventing Holliday from taking a live batting practice session to test it out. ... On Monday, Cincinnati RF Steve Selsky produced the franchise's first five-hit game for a rookie since Wade Rowdon had one on July 9, 1986, against the New York Mets. ... Cardinals 1B Matt Carpenter (hand) returned to the lineup Monday in his normal leadoff role.