Maas Is Playing It by the Numbers : Baseball: Yankees’ amazing rookie steps in for the injured Mattingly and rewrites the major league record book.

ANAHEIM — Kevin Maas signed the last baseball, finishing off a boxful, and stood aside for Steve Sax to take his place at a table in the Yankee clubhouse.

“Who’s he?” Sax said, tossing his head in Maas’ direction, where a baseball card representative had intercepted him. “Yeah,” Sax said, turning back to the baseballs, “Put the (guy) in the Hall of Fame.”

The razzing comes with the stats. Kevin Maas, a 25-year-old rookie who has stepped in at first base for the injured Don Mattingly, hit 10 home runs in his first 77 at-bats with the New York Yankees.

No one in major league history had reached 10 homers more quickly.

Maas hit a homer July 4 in his 15th major league at-bat, off Kansas City’s Bret Saberhagen. He hit homers in three consecutive games, July 23-25, all against Texas.

He hit his 12th homer off Seattle’s Erik Hanson, becoming the 21st player to hit a ball into the Kingdome’s upper deck, an estimated 448-foot shot.

After 100 at-bats, he had 12 homers, tying a major league record.

After 110, he had 13, another major league record.

“I’ve been in stretches like this before,” Maas said. “They don’t happen all the time, though. Not even once a year. It’s not a fluke, put it that way.”

As he prepared for one of the Yankees’ games against the Angels at Anaheim Stadium this week, Maas finished another piece of business and made his way to his stall, where a few reporters waited. Greg Cadaret, a Yankee pitcher whose stall is a few yards away, sniffed at the attention.

“What did you do? You haven’t even played yet.”

Maas laughed.

“That’s part of it,” he said. “You take it in stride. I can turn one cheek with the best of them.”

Maas, a Cal graduate with a degree in mechanical engineering, is adding a bit of suspense to a season that has been unsuspenseful for the Yankees, at least on the field.

In his first at-bat Monday at Anaheim Stadium, Maas hit a fly to the warning track in right field, where it was caught by Dave Winfield.

There’s a reason they call them homers. A left-handed hitter, Maas has a swing that is built for Yankee Stadium, where the right-field foul pole is only 310 feet from home plate, and right field is 353 feet away.

Seven of his homers have come at Yankee Stadium, one in every 7.4 at-bats.

Even when Maas was playing at double-A Albany in 1988, people already were thinking about it. It didn’t seem to matter that Mattingly stood entrenched at first base, Maas would find a place in the Bronx.

“I figured Yankee Stadium was the perfect place for him,” said Deron Johnson, the Angels’ batting instructor who was then coaching at Albany. “He has a nice, short swing and real strong hands. . . . He worked real hard. He knew where he wanted to go.”

Now, quickly, it seems, he is there, and everyone seems to want a piece of him.

“It’s been pretty crazy,” Maas said. “That’s an understatement. . . . My days become very short. By the time I wake up to the time I go to bed, it seems like a couple of hours. I’ve been so busy, whether it’s been calls from the media, friends, family. I’m certainly trying to stay focused on baseball.”

Baseball: In 36 games before Tuesday, he was hitting .271 with 13 homers in 118 at-bats, with a slugging percentage of .619.

“It’s not like I’m just breaking into the big leagues,” Maas said, as if making a concession. “I’m doing it like gangbusters.”

The question is whether this is the beginning of a long and enduring career or the start of one that will be buried in the Baseball Encyclopedia, along with his name.

For now, Maas has hit a homer every 9.1 at-bats.

Babe Ruth hit one every 11.8 at-bats over the course of his career; Ted Williams one every 14.8; Willie Mays one every 16.5; Hank Aaron one every 16.3; Carl Yastrzemski one every 26.5.

That is some of the company the stats draw.

The names of the people whose records he has broken give cause for reflection.

The 10-homer record was held by George Scott, who needed 79 at-bats with Boston in 1966 to hit his first 10 home runs. He hit 27 homers that season in 162 games. In the best year of his 14-year career, he hit 36 for Milwaukee in 1974.

The 13-homer record belonged to Baltimore’s Sam Horn, who needed 123 at-bats to reach that mark in 1987.

Mass is tied for most homers in a first 100 at-bats with Texas’ Dave Hostetler, who did it in 1982.

Some names and numbers flatter, some do not.

“You don’t build a career in a month-and-a-half,” Maas said. “You build it by doing it every day. . . . I’m really trying to play down what I’ve done. I still feel I have to prove myself every day.”