The Houston Astros, milking the publicity involved to the fullest, have scheduled a Monday press conference "on the Ryan situation."

Then the Astros finally will announce what has been an open secret for three days: Nolan Ryan, 32, the fireballer who pitched for the California Angels last season, will sign with Houston at a price of $4 million, $1 million a year.

Everyone connected with the situation was issuing nondenial yesterday, including Dick Moss, Ryan's agent, who said, "I can't deeply deny the obvious."

Ryan lives in Alvin, Tex., 26 miles from Houston, and it had been reported throughout the 1979 season that he would sign with the Astros after playing out his option with the Angels.

Ryan holds the single-season record for strikeouts (386) and is tied with Sandy Foufax for the record for no-hitters with four.

The Boston Red Sox appear to have come up with a replacement for first baseman-designated hitter Bob Watson, lost to the New York Yankees in the free-agent draft last week.

The Red Sox signed Tony Perez, 36, the Montreal Expos' veteran first baseman, to a three-year contract yesterday.

Perez, a career .283 hitter, has 2,238 major league hits, 323 home runs and 1,357 RBI. He played 12 of his 15 big league seasons with the Cincinnati Reds and was a key member of the Reds' 1975-76 world championship teams.

Baltimore Oriole relief ace Don Stanhouse has narrowed his list of teams to five, his agent said. According to Cookie Lazarus, Stanhouse's negotiator, the teams still in the running for the free-agent right-hander's services are St. Louis, Los Angeles, California, Milwaukee and Philadephia. Lazarus added that he has not heard from the Orioles since the draft.

Baltimore General Manager Hank Peters said he plans to call Lazarus this weekend and is very interested in trying to keep Stanhouse, 7-3 with 21 saves and a 2.85 ERA last season with the Orioles.

The Atlanta Braves yesterday said they had come to terms with relief pitcher Al Hrabosky, the "Mad Hungarian" who played out his option last season with Kansas City.

In Anaheim, Calif., the Angels said that pitcher Bruce Kison, who played out his option last season with the Pittsburgh Pirates, has agreed to terms and will sign a five-year contract.