Mike Greenwell used to perch in the trees outside Terry Park, the Kansas City Royals' old spring-training ground in Fort Myers, Fla.

His high school team, the North Fort Myers Red Knights, played on an adjacent field and so Greenwell used to climb a tree and watch George Brett, Hal McRae and Willie Wilson. Especially Brett."They had a lot of great players on that team," Greenwell said, "but I was a third baseman in high school and, since he was a third baseman and a left-handed hitter, he was just kind of a natural role model for me."

A natural, all right. Today, Greenwell's major-league career average is .331; the model's mark is .313. Of course, Brett is about 13 years and more than 2,000 hits ahead of Greenwell.

Greenwell has graduated from the Red Knights to the Red Sox. He is Boston's left fielder and cleanup hitter and one of baseball's rapidly rising stars.

"The statistics prove it," Brett said.

The statistics show: after four years of minor-league seasoning, Greenwell arrived in Boston in late 1985 and hit .323 in 17 games.

After another half-season in the minors in 1986, he was recalled by the Red Sox and hit .314 in 31 games.

As a rookie last season, he got his first full shot and hit .328 in 125 games and had 19 homers and 89 runs batted in.

"He had a trying time last year at the start of the season," Red Sox manager John McNamara said. "But when we weren't going anywhere at the All-Star break - that's when we released Billy Buckner and gave him the chance to play. He can hit. There was never a doubt in anybody's mind."

The kid from North Fort Myers showed everyone that right at the beginning, in '85 when he was fresh from Class AAA Pawtucket, R.I.

His first three major-league hits were home runs. The first was a two-run, game-winning shot in the 13th inning in Toronto. The next was another two-run game-winner against the Blue Jays. The third came in Baltimore.

"When I hit the third one, I knew it was gone. I knew it was going to be way out of the ballpark," Greenwell said. "When I started to go down the line, I glanced over my shoulder. At that time, the team was mostly all veterans, guys who'd been around a long time. It was great to look over there and every one of them was standing on the top step, watching the ball.

"It was a great feeling for me because I knew all those guys were behind me. They were as excited as I was. A lot of the older guys teased me that they'd been around 12 years and I come in and get three hits and I'm in the record book. So that was kind of neat."

Greenwell was accepted and appreciated, but the Red Sox had no spot for him, not with such players as Jim Rice, Dwight Evans, Don Baylor, Buckner and others filling the lineup. Besides, in '86 the Sox were preoccupied with a pennant drive. Greenwell did come up in late July and gained a spot on the postseason roster. He pinch hit four times in the World Series against the Mets. But not until Buckner left did he have a secure spot.