The semicircular space at the west end of the Polo Field could efficiently accommodate two baseball fields (shown in light blue on the map) separated by a tall fence (shown in yellow). Another tall fence could stand between the fields and the baseball grandstand (shown in dark blue), which would shield both fields from errant soccer balls. Both fences would need padding along the bottom 8 feet or so. The outfield fence would need to be raised to shield bicyclists from home run balls. Dugouts could be built into the grandstand, and bullpens to its north and south.
If a polo field were ever needed, the grandstand would still allow a full-size ground (300y x 160y) to the east (using part of the cricket field), with an ample 30+ yards of separation (the existing soccer fields would have 15 yards of separation). A grassy berm between the soccer fields and the grandstand would make it easy for soccer players and horses to come to a stop well short of the grandstand.