The Cardinals had a runner at second and two outs in the eighth when Diaz hit the comebacker to Grimm, who spun and calmly gloved the ball, then threw to first. It was just one more highlight in the victory.
Cubs starter Jason Hammel liked it, posting on Twitter: "If @GrimmReaper_52's play is not a #WebGem tonight ... #heshouldveseenit."
"I'm sure he practices that in the offseason in his living room," manager Joe Maddon said. "He's one of those guys definitely capable of bizarre in the bizarro world that he lives in."
But Grimm said he's never practiced a between-the-legs play like that.
"I've attempted it, yeah, because I've had a lot of balls hit back at me," he said. "I never was able to pull it off."
In Spring Training the pitchers are prepped for such situations, Grimm said.
"They do hit these balls at us at 100 miles an hour, but you don't have time to turn around," he said.
Grimm was eager to see a replay.
"Mark it off the bucket list," he said.
Carrie Muskat has covered the Cubs since 1987, and for MLB.com since 2001. She writes a blog, Muskat Ramblings. You can follow her on Twitter @CarrieMuskat and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.