The Major Indoor Soccer League, ever its own best promoter, will open its seventh season tonight with eight of the league's 14 teams in action, including the league champion Baltimore Blast, which will begin defense of its title in Pittsburgh at 8:05.

Although the outdoor version of the game as played in the North American Soccer League has met with apathy from the public, indoor soccer has gained wide acceptance, helped by fireworks and sound and light shows.

League attendance was 2.8 million last season -- including near-capacity crowds for the final series, in which the Blast won four straight from St. Louis after losing the first game at home.

One of the leaders in attendance last season was the Blast, whose spaceship and smoke show before games became as much a team trademark as the solid coaching of Kenny Cooper and the scoring of Stan Stamenkovic, the league's most valuable player. With 5,500 season tickets sold and a revamped pregame show, Baltimore again figures to be among the league's most exciting teams -- on and off the floor.

Led by Stamenkovic (a league-high 97 points), Paul Kitson (36 goals) and Dave MacWilliams (33 goals, 32 assists), the Blast finished as the league's best power play team.

The Blast also has a strong defense. With all-star defender Heinz Wirtz and goalkeeper Scott Manning, Baltimore was among the league's best in killing penalties. In the championship series, Manning shut down the Spirit in the third and fourth games with 30 and 25 saves, respectively.

The second half of the Blast's goalie pair, Keith Van Eron, signed in the offseason with Las Vegas. That left former all-star Jim May, a free agent from Buffalo, as Manning's alternate.

But while overall stability has been maintained in Baltimore, the league is in transition. The Memphis franchise has relocated in Las Vegas, Dallas has been granted an expansion franchise and New York, Phoenix and Buffalo have been absorbed. Also, the MISL added four North American Soccer League teams -- Minnesota, San Diego, Chicago and the Cosmos -- since that league ceased playing indoors.

(The four teams still are members of the NASL and have the option of returning to outdoor play in June. San Diego and Chicago are not expected to return to NASL play, even though the Sting won the league's outdoor championship last month, according to a league spokesman.)

Based on last weekend's league invitational tournament and past history, San Diego appears to be the toughest of the Blast's competitors. The Sockers have won three straight indoor championships -- two in the NASL and the MISL championship in 1982-83. The team did not compete in the MISL last season. Chicago, which won the NASL outdoor title last month, competed in the MISL in 1982-83, also.