(Updated June 9, 2020)
Tim McCarver and Terry Pendleton each hit an inside-the-park grand slam for the Cardinals against the Mets on the same date, 22 years apart.
Each occurred on June 9 in New York in the second game of a Sunday doubleheader.
McCarver hit an inside-the-park grand slam June 9, 1963, in the Cardinals’ 10-4 win over the Mets in Game 2 of a doubleheader at the Polo Grounds.
Pendleton hit an inside-the-park grand slam June 9, 1985, in the Cardinals’ 8-2 win over the Mets in Game 2 of a doubleheader at Shea Stadium.
Both occurred because of outfield misplays.
Slipping and sliding
The Cardinals led, 6-1, in the eighth inning when McCarver batted with the bases loaded, one out, against Mets rookie reliever Larry Bearnarth and laced a line drive to center.
“I was just figuring on a sacrifice fly,” McCarver told The Sporting News.
Center fielder Rod Kanehl got to the ball and, just as he appeared ready to make the catch, slipped and fell. The ball darted past him and rolled to the wall, 475 feet from home plate. McCarver raced home with his second big-league home run. It was the first grand slam he’d hit at any level of competition.
Cardinals center fielder Curt Flood empathized with Kanehl, informing the St. Louis Post-Dispatch, “The turf is loose and the grass is slippery out there. I slipped three or four times running when the ball wasn’t even hit to me.” Boxscore
Communication breakdown
Like McCarver, Pendleton was looking to extend a Cardinals lead when he came up against Mets reliever Joe Sambito with the bases loaded and one out in the fifth inning. St. Louis led, 4-0.
Pendleton hit Sambito’s first pitch to right-center. Right fielder Danny Heep and center fielder Terry Blocker gave chase.
“At first I thought, ‘Good, we’ll get a run on a sacrifice fly,’ ” Pendleton told the New York Times. “Then I looked in the outfield and saw them flying at each other, not slowing down.”
As Blocker was reaching for the ball, he and Heep collided, and the ball caromed off Blocker’s glove. “We both called for it, but I didn’t hear him until the last second,” Heep said to the New York Daily News.
“I could see it coming,” Cardinals manager Whitey Herzog said to the Associated Press. “Neither one of them knew if they could catch the ball.”
Blocker lay motionless. Heep recovered, retrieved the ball and got it to first baseman Keith Hernandez, whose relay throw was too late to nab Pendleton. Boxscore
“I thought one of them would be able to get up in time,” said Pendleton. “I thought I had a shot at a triple.”
Becker injured both knees and was carried from the field on a stretcher.
“It’s a hell of a way to get a grand slam, isn’t it?” Herzog asked.
RetroSimba 
Let’s not forget that our beloved former catcher, years later, would accomplish another rare feat. A ” grandslam single” on July 4th, 1976.
Indeed. Playing for the Phillies against the Pirates, Tim McCarver, batting with the bases loaded, hit a pitch over the fence, but instead of a grand slam, he was credited with a three-run single because he was called “out” for passing a runner, Garry Maddox, on the base path. The boxscore: https://www.retrosheet.org/boxesetc/1976/B07041PIT1976.htm
I saw the Mets game on TV. It appeared that the ball landed a foot beyond the prone Kanehl’s cap, and just kept rolling. I loved that ballpark.
Thanks for the first-hand account. Polo Grounds is where I saw my first major-league game in 1963. It always will remain a special place for me, too.