I also discovered that I'm also not nearly as agile at tennis as I once was. We got out onto the court recently with the elementary school aged boys, who had never played tennis before. I was about like you'd expect, including a few times when the ball was lobbed over my head. As I turned and started heading back to the baseline, I realized that at one time it would have been easy to make that shot; and now I wasn't going to get there in time. Walking is hard enough. Running in a straight line is tough, and making a turn takes a lot of concentration. Running while looking over my shoulder and needing to move to one side or the other is almost disastrous (if falling and scraping my knee is a disaster).
Someone recently asked me if, early on in the post-accident recovery, riding a bike was easier than walking. At that time I had to strap a crutch to my bike so that I could walk when I got where I was going. So, yes. When I first got on a bike again, cycling was easier than walking. In fact, even now cycling is easier for me than walking. When I'm on a bike, I can just ride. When I'm walking now, if I want to not stumble, I generally have to consciously think pretty specifically about which muscles to engage.And walking is certainly easier than playing tennis, or baseball, or basketball, or soccer, or racquetball, or volleyball. But I had fun on the tennis court. And it might be fun to try any of those other games again, too. I guess that means I have to add some agility work back into my fitness routine.