Yesterday, the hurt of baseball's strike set in.

It has not immediately hurt the players; they will receive paychecks for their work during the past week. It has not yet hurt the owners; they have strike insurance that could probably carry them at least until season's end.

But those caught in the middle, those who have nothing to do with the negotiations or the dispute, felt the pain sink in yesterday.

In Baltimore, head groundskeeper Pat Santarone had to lay off four of his seven assistants until a settlement comes about. The 18-man tarpaulin crew was told there will be no work Tuesday when the Orioles are supposed to return home for 10 games. The 80-man maintenance crew that cleans Memorial Stadium after each game faced the possibility of going without work until the Colts begin playing football.

All over the country, front office staff were scrambling. Many fans wanted to know about refunds and exchanges on tickets. The Orioles decided to wait until Monday before announcing plans. The Boston Red Sox announced they would issue immediate refunds on tickets. The St. Louis Cardinals decided to treat the games like rainouts.

The moaning may have been loudest in Philadelphia. As many as 60,000 fans had been expected for Friday's game with the Atlanta Braves in anticipation of Pete Rose breaking Stan Musial's all-time National League record for hits.

Joe Ralph, Philadelphia's assistant recreation commissioner, estimated that the city will lose a minimum of $78,700 in taxes from ticket sales for each game that is canceled.

"That estimate could be low," he said. "With the Phillies as hot as they are and Rose going for the record the Atlanta series might have drawn 150,000. That would mean we lose more like $120,000 a day."

Last year, according to Ralph, Veterans Stadium generated about $2.4 million in profits for the city. Without baseball, he said, the city could lose money on the stadium for 1981.

And 1,200 part-time employees of the Philadelphia ball park -- ticket sellers, ushers, parking lot attendants -- will be out of work until the strike is resolved.

On the average, each day without baseball will cost a team around $100,000, if estimates being released by the 26 clubs are accurate.

But the timing of the strike hurts some more than others. In Minnesota, the moribund Twins are expecting their biggest crowds of the season with the Yankees in town for three games.

Club President Calvin Griffith said yesterday that the Twins had expected about 100,000 customers for the three-game series -- the Twins are averaging under 7,000 per home game -- and so figure to lose about $600,000 in gross income.

Things are so tough in Minnesota that the Twins might have to take out a loan to survive a long strike. Even worse, Griffith said he might have to take a cut out of his own salary, estimated between $125,000 and $150,000.

Griffith's woes hardly seemed major when compared with people like John Molinaro, a New York City stock clerk who supplements his living by selling beer at Met games.

"How am I going to live through this?" he asked. "I need both my jobs just to live. I don't care about issues, man, I care about living."

The Oakland A's were devastated not so much by financial losses but because they expected to pass last season's total attendence this weekend.

"We had a good chance to have the second-largest attendence increase in baseball history this season with a full schedule," Andy Dolich, A's vice president, said."Now, every game we lose (don't play) makes it that much harder for us to do something like that. We could see a lot of hard work by a lot of people wiped out."

From another angle on the A's, $12-a-day batboy Steve Holt was more upset by not being around baseball than by loss of revenue. "I don't make that much money but I love being around the game," said Holt, 19. "I guess most people don't realize that this puts a lot of people out of work, not just the players."

Some players will hurt more than others. For instance, Montreal Expo rookie Chris Smith, only lately recalled, will find himself without paychecks if the strike lasts beyond Monday. If he had stayed in the minors he would be playing and getting paid.

"This is going to kill me . . ." Smith said."I wish they'd sent me back down in some ways, especially financially."

One group not affected by the strike: the umpires. Under the contract that followed their own strike two years ago, they are guaranteed up to 45 days' pay even without any games to work.

Finally, there are the fans. Most teams kept their advance ticket windows open and reported some business, although not nearly as much as normal. Many fans bought tickets for games in August and September, figuring a settlement would be reached by then.

While players paid their own ways home and pondered their futures; while part-time, low-salaried employes wondered where their next dollar would come from; while fans wondered when their next day at the ball park would come, Dick Wagner of the Cincinnati Reds, a chief executive who recently fined Dave Collins $50 for tossing a baseball to a fan, said:

"I just can't believe people strike. Not people making $225,000 a year -- that's the National League average -- for seven months' work. It's just inconceivable. In certain ways, our game is sinking to the level of the rest of the country."