https://www.baseballthinkfactory.org/bt ... atfldg.htmIt depends on how much offense the 4 fielder generates compared to the runs he allows in the field.
The above chart is how much OPS a defender allows on average. add the two per game totals.
On the offensive card--look at the color chart on the bottom of the card... add 1 for BB/HBP, 2 for SI, ... to 5 for HR.
this is OPS (On-base + Slugging) in card chances. Subtract the number from the fielding chart above (which is OPS allowed)
This gives you a way to compare Offense minus Defense, A 3RF and a 4RF of similar cost for instance.
IF the offense adds up to 100, but defense allowed is -40--that is 60 net. A two guy may have only 80 offense but just allows -15 in defense--so it is always a compromise.