Tennis is also an outdoor sport that allows you to keep distance while getting a great workout, but the outdoor part may or may not be applicable in the winter depending on where you live.
Good point. One nice thing about rec sports like soccer is there's usually a division for people who absolutely suck (or are novices). Tennis is a bit more frustrating when you and your opponent are grossly mismatched (for both players). Soccer can still be fun unless you're on a team of klutzes.