When the Detroit Tigers' Jack Morris beat the San Diego Padres in Game 1 of the World Series Tuesday night, it was not so much his fast ball -- although it is a good one -- as his split-fingered fast ball that kept them off balance.

"When he throws that thing well, combined with his good fast ball, he's pretty tough," San Diego center fielder Bobby Brown said. "I don't remember him throwing it that well when I was in the American League."

That's because Morris didn't throw it that well until two years ago. Then, he became one of several Tigers who learned it from their pitching coach, Roger Craig. Now, seven of the nine pitchers on the staff throw it.

"I threw it a little when I pitched," said Craig, who lost 18 games in a row for the 1963 New York Mets. "But I never could learn to teach it. But then in 1981 I was working with some kids at my baseball school and I got it working. I figured if I could teach it to kids I could teach it to major leaguers."

Craig's first student was Milt Wilcox, who will pitch Game 3 in Detroit Friday. Others who then began learning it included Morris and tonight's starter, Dan Petry.

"That pitch and the work Roger's done had as much to do with our success as anything," Manager Sparky Anderson said. "He's really helped our pitchers."

Only Aurelio Lopez and Willie Hernandez, who throw screwballs, do not throw the pitch, which drops like a hard sinker. It drops so much, some have said pitchers who throw it load the ball up. George Brett specifically raised the question about Morris last week in Kansas City.

The Detroit organization is so grateful to Craig for his work that it has reportedly offered him a two-year contract that would make him the highest-paid coach in baseball. He had planned to retire after the season. "I have to think about it," he said. "In July, I was 100 percent sure I wanted to retire. Now, I'm not."

The most surprised man in uniform at this World Series is San Diego pinch hitter Ron Roenicke. He spent most of the season playing at Las Vegas and was called up in September. He was activated for the World Series after Kevin McReynolds broke his arm Saturday against the Cubs.

"I don't really feel the same as the other guys because I didn't struggle to get here the way they did," Roenicke said today. "I didn't play most of the season or the playoffs. So, it's not the same for me."

He isn't complaining. In 1981, when he spent the season with the Los Angeles Dodgers, he was injured just before the end of the regular season and had to sit out the playoffs and World Series, which the Dodgers won.

"This makes up for that a little bit," he said. "This is like a shock, standing here being part of this."

San Diego Manager Dick Williams is toying with the idea of letting Tim Lollar hit for himself when he pitches Game 3 in Detroit Friday.

Lollar was an all-America designated hitter at Arkansas in 1978 and did not start pitching full time until after signing with the Yankees in 1979. He has hit eight career home runs, including three this year. He also drove in 15 runs this year and might be a better hitter than Kurt Bevacqua or Champ Summers, whom Williams had picked to DH.

"I'd like to hit," Lollar said. "I like to still think I'm a pretty good hitter. Whatever Dick wants, though, is fine."

President Reagan, campaigning in the Detroit suburbs today, told a gathering of high school students in Redford, Mich., he "can't take sides" in the World Series.

"I was thinking -- maybe I'll cheer for the Padres and pray for the Tigers," he said.

Hank Peters, general manager of the Baltimore Orioles, was released this morning from a hospital where he was taken after collapsing during a postgame reception following Game 1 of the World Series.

"He's just fine," said an Orioles spokeswoman in Baltimore who asked not to be identified. "He was just fatigued."