Opposing baseball teams playing a game.
The team is playing.
Opposing teams playing a game implies there are two teams, so at least one team is playing.
exists e1 e2 x1 x2 x3 x4.(a_topic(x1) & Theme(e2,x4) & Actor(e2,x3) & v_play(e2) & n_game(x4) & (x1 = x3) & n_team(x1) & of(x1,x2) & n_baseball(x2) & Actor(e1,x1) & v_oppose(e1))
exists e1 x1.(n_team(x1) & Actor(e1,x1) & v_play(e1))