CHARLOTTE, N.C.- It took Mike Greenwell 10 years to go from the Green Monster of Fenway Park to the green flag of NASCAR racing.

The former Red Sox outfielder hung up his glove in 1996 eager to start a new athletic endeavor – racing cars. After a decade spent toiling around in late models, Greenwell will finally make his NASCAR debut in Saturday night’s Truck Series event at Mansfield (Ohio) Motorsports Speedway.

“I retired very early,” Greenwell said. “I hit .297 my final year and I had 20 offers to go back and play the next year. But I wanted to go racing. I literally quit baseball so I could go racing.”

Greenwell, who hit .303 with 1,400 hits and 130 homers 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 grassroots stock car level.

He wasn’t bad, either, winning 37 races and the 2000 speedweeks championship at New Smyrna (Fla.) Speedway. But he wanted to test his skills against the best, and his longtime friendship with Truck Series driver Todd Bodine opened the door for him.

Greenwell grew up a racing junkie, and got to know Bodine while following the sport during his playing days in Boston.He became a frequent visitor to tracks around the Northeast, and was delighted when New Hampshire Inter national Speedway opened in 1990 and began hosting NASCAR events.

Racing was foreign to his clubhouse cronies, but Greenwell worked hard to get his teammates to follow the sport.

“I was such a fan, I would tape the races and I actually got a lot of the guys interested because of that,” Greenwell said. “Then when the Bahre family opened the track in Loudon, there was so much press about it and it was really cool to the see the fanatic fans of New England become interested in racing.”

Greenwell stayed in touch with Bodine when he launched his racing career, and the relationship helped him meet several other drivers and contacts in the sport. Bodine had coaxed him to test in a Busch Series car, and finally found the right opportunity for him this season in a truck owned by Bobby Dotter.

If his debut goes well, Greenwell has plans to run two more events this season – including a return to New Hampshire in September.

Bodine has no doubt Greenwell will be a success, and insists he’ll do better than former NFL coach Jerry Glanville, who had a brief, sub-par stint as a driver.

“Mike’s real good, he’s a racer who understands about driving,” Bodine said. “He’s won a lot of races before and championships. He’s not a Jerry Glanville, a guy who came in here wanting to be a racer and didn’t know what he was doing.”

But Greenwell doesn’t have any grand illusions of wowing the field Saturday night with a win.

“I am hoping to go there and be competitive and finish the race,” he said. “It’s my first race against these guys, and there is probably going to be more nerves than any other race I’ve ever been in. Am I going to be able to just run laps? No. I am going to have to race, and I hope to finish it.”

Greenwell doesn’t know what’s in his racing future beyond this three-race stint. He’s 42 years old, and knows he’ll probably never make it to Nextel Cup racing. But a Busch race or two isn’t so far-fetched, nor is putting together a schedule of truck races.

But Greenwell doesn’t want to do too many races that take him away from home. He said his two teenage sons are excellent athletes, and he expects 17-year-old Bo to be selected in the Major League Baseball draft.

“This is more like fulfilling a dream for him,” Bodine said. “He has his family, and I’m not sure he wants to do this full-time. But in the future, maybe he can be part of the sport as a car owner, or a truck owner and maybe he might run three or four races a year to have some fun.”