Guardiolas side was built to probe deep sitting defenses without risking counters and in (rare) open games would starve the opponent of possession and use the passing game to wear the opponent out who would have to chase the ball. Before 2006 an opponent would simply make the field compact and flood the midfield with players, trusting on the off side trap against counters. Barcelona would not be able to gain numerical superiority there, there would be much less space for the passing game and would struggle in terms of physicality. The typical early 2000s sides like Ancelotti's Milan, Mourinhos Chelsea and Wenger's Arsenal would have overpowered them in midfield under the old rules. Guardiola himself, a Xavi like passer, was literately muscled out of the game by the late 90s. Bayern use hard pressing (and possession to lesser extent) to play a high line.