I'm still confused about how you factor an infinite amount into a teams pitching stats.
here's how things work, stat-wise.
say your staff has an era of 4.5 (not great, but easy to work with mathematically) and this comes from your pitchers having pitched 50 innings and giving up 25 runs.
now graves comes in and gives up 2 runs in no innings, therefore your staff has still pitched 50 innings but you have now given up 27 runs.
his era for the day is 9*2/0 = infinite
your era for your staff is 9*27/50 = 4.86
hope this helps