SAN DIEGO -- In the final days, Mike Schmidt 's mind wandered. At Dodger Stadium a week ago, where the Phillies began what would be his last road trip, he compared his fading skills to Kirk Gibson. When the action shifted to Candlestick Park, the measuring sticks were Will Clark and Kevin Mitchell.

"I was wondering if I could compete with those guys anymore," Schmidt said yesterday. "I'm watching them and feeling like a shadow of the player I used to be.

"And that was telling me it was time to turn the reins over to somebody else."

So by the time Sunday's game in San Francisco was over, a firm decision had been made. Schmidt , issued a walk by Mike LaCoss in the ninth inning and left stranded at second, walked slowly off the field. He went to the clubhouse and took off his Phillies uniform, the only one he ever wore in the major leagues, for the last time.

After 18 seasons, 2,404 games, 2,234 hits and 548 home runs, it was over.

Mike Schmidt , the best player in Phillies history, the greatest third baseman ever to play the game, a certain first-ballot Hall of Famer, was going to retire.

He told Phillies manager Nick Leyva on the team's charter flight to San Diego. He asked Steve Bedrosian to gather his teammates when they arrived at their Mission Valley hotel.

Leyva contacted club president Bill Giles and general manager Lee Thomas.

The formal announcement was made two hours before last night's game against the San Diego Padres, in a vacant football clubhouse.

And while the timing at first seemed curious - why not at least wait until the Phillies returned to Veterans Stadium this weekend? - Schmidt 's explanation was elegantly simple.

It wasn't because of various aches and pains, wasn't because of his shoulder or his elbow or his knees.

It wasn't because the Phillies had lost nine of 11 to sink to the of the National League East.

It wasn't even because of a 2-for-40 slump that had lowered his batting average for the season to .203, or the fact that he had hit only one home run since April 23.

It was because the game had become hard for him. And that made his decision easy.

"Over the years of my career, I've set high standards for myself as a player," he said in a prepared address that was interrupted at least three times when the supposedly unemotional Schmidt broke down and cried.

"I've always said that when I don't feel I can perform up to those standards, that's when it would be time to retire.

"My skills - to do the things on the field, to make the adjustments needed to hit, to make the routine play on defense and run the bases aggressively - have deteriorated. "

Later, speaking more informally with a half-dozen Philadelphia area reporters, Schmidt elaborated on those feelings.

"I got to the point where I was wondering if I could compete with players like Gibson and Clark and Mitchell," he said. "I had been thinking about this for a while. I went four or five days longer than I really expected to.

"I kept waiting for it to turn around on the field. But it never did. I kept thinking out there that this would be my last game. Then this would be my last game. Then this one would.

"And it got me into kind of a funk because my mind was not into it and I wasn't helping the ballclub. "

And now the ballclub that was graced by his considerable presence in the cleanup spot for so many years will have to get along without him.

He planned to get up well before dawn this morning to appear on NBC's ''Today" show, then fly back to Philadelphia.

He will throw out the first pitch before Saturday night's game against the Expos. Later in the summer, his familiar No. 20 will be retired with the appropriate pomp and ceremony.

Meanwhile, the Phillies begin Life After Schmitty.

Chris James becomes the everyday third baseman. For the time being, a platoon of Bob Dernier and whichever of the lefthanded-hitting outfielders (Dwayne Murphy, Curt Ford or Mark Ryal) is hot will replace James in left.

And the roster spot will remain vacant until Friday when the Phillies will call up a player from Triple-A Scranton/Wilkes-Barre, unless they can acquire a utility player from another organization.

The focus had been on Schmidt since last September, when he went against the team's recommendation and had arthroscopic surgery on his right shoulder. Club physician Dr. Phillip Marone and two other doctors had suggested full surgery to repair a partially torn rotator cuff, a procedure that can't be done arthroscopically.

At age 39, coming off surgery, Schmidt paced himself through spring training. Some wondered if he had anything left. He got off to a fast start, though, by hitting five homers in the Phillies' first 17 games.

After that, however, the long slide began. And by the time Schmidt made his retirement official, few of the people around him were shocked.

Giles, who had stayed in northern California Sunday night, got a message to call Thomas when he returned to his room around midnight.

"I wasn't surprised," Giles said. "Nick Leyva had told me Schmitty made some comments in Los Angeles about playing every day for a few days and then seeing what happened.

"Knowing Mike as well as I do, I knew he had the feeling that he didn't want to stick around unless he could perform at the level he had become accustomed to. "

Leyva, too, could see the signals.

"You could see in his face that he wasn't happy," Leyva said. "It was completely different from the way he was early in the year when things were going well.

"This man has a lot of pride. He just felt it was time, and I respected that. He just feels he's not doing the job anymore. I thought in April he had a chance to have a pretty good year, but a lot of times that can be adrenaline and it catches up with you. "

By retiring now, Schmidt walks away from at least $500,000 he could have collected if he was still on the roster Aug. 15. And he would have received $150,000 for starting 130 games and another $150,000 if he started 140 games.

He already had made $1 million for signing and remaining on the roster until May 15.

Phillies coach John Vukovich, who played several seasons with Schmidt , said this proves that Schmidt never was as emotionless as people believed.

"How many people would turn their backs on that kind of money? " Vukovich asked. "To me, what he did was to show the doubters that, down deep, he really has a lot of pride."

It was that pride that moved Schmidt to speak to the team Sunday night.

"I wanted to do that, because I didn't want them to think I was quitting on them during a tough time. Quit is a word I don't want associated with my name," he said.

"I told them a lot of good things could happen. Guys are going to get to play every day. "

Schmidt appeared more relaxed than he has in recent memory.

"I might be the happiest person in the stadium," he said. "When you wake up in the morning and you're a lot happier to be a former player than you were to be a player the morning before, you know you've done the right thing.

"I can't tell you how relieved I am. It's hard to put into words. But when you're used to doing something and being one of the best, then you see somebody replacing you at the top, you fight like hell against it.

"So I gave it six games, seven, eight, nine, 10. And it just wasn't there. "

Reds manager Pete Rose, a former teammate who often has been credited by Schmidt for giving him the confidence needed to win three Most Valuable Player awards, said yesterday he thinks things might have been different if Schmidt had accepted the Reds' offer of $1 million to play in Cincinnati this season.

"I hate to see him retire," Rose said. "He hasn't gotten off to the kind of start he wanted to.

"I still think he would have been better off coming here. I think Mike needs to be on a good team, a team that has a chance to win. "

Schmidt , while stressing that he wasn't blaming the rest of the team for his decision, conceded that he might have reconsidered if things were going better for the club.

"I have to admit that, if we were in first place, some of my homers and some of my runs batted in would have contributed to our being there," he said.

"It's hypothetical, but if that were the case, I wouldn't have had all this mental anguish. And I probably wouldn't have retired. "

Schmidt said there was no watershed moment, no flash of insight that told him when he was through.

"It wasn't one play, but really a whole series of events on this West Coast trip," he said. "It was probably more a sense of my inadequacies defensively than anything else. "

Schmidt took a few questions in the crowded room, then left. It was the first day of the rest of his life.

A few feet away, in the Phillies' clubhouse, equipment manager Frank Coppenbarger was cleaning out Schmidt 's locker.

(Note: This story was originally published on May 30, 1989.)