The crowd is gathered to watch a sporting event.
A single person is playing tennis against a brick wall.
A crowd is comprised of multiple people, not just a single person. Playing a sport is active involvement and to watch is to passively observe.
exists e1 p1 x1.(n_crowd(x1) & Recipient(e1,p1) & Topic(e1,x1) & v_gather(e1) & exists e2 s1 x2.(Theme(e2,x2) & Actor(e2,x1) & v_watch(e2) & n_event(x2) & a_sporting(s1) & Theme(s1,x2)))
exists e1 s1 x1 x2 x3 x4.(against(e1,x3) & n_wall(x3) & of(x3,x4) & n_brick(x4) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_tennis(x2) & n_person(x1) & a_single(s1) & Theme(s1,x1))