The former Red Sox outfielder hung up his glove in 1996 eager to start a racing career.
He will finally make his NASCAR debut in Saturday night's Truck Series event at Mansfield Motorsports Speedway in Ohio.
Greenwell, a career .300 hitting in his dozen years with the Red Sox, wasted no time switching gears. He returned to his home state of Florida and jumped into the Saturday night scene, racing at the grass-roots stock car level.
He has won 37 races and the 2000 Speedweeks Championship at New Smyrna Speedway in Florida.
If his debut goes well, Greenwell has plans to run two more events this season — including a race in New Hampshire in September.