Super easy! Do a Custom Season with 4 custom teams (1 MAX 99 team and 3 bad 0 rating teams). To save time I created one bad team and copied it twice. Go to Season and set it for 200 games (Mine was overkill at 200 but it worked) and simulate the whole season (Simulate 199 games then simulate the last game to get to the end, as simulating to the playoffs directly doesnt unlock it). All my pitchers ended up with ERAs under .5 and all batters except one was over .400.