I've accepted that a little off time is a good thing for me now. My trainer suggests that I may be suffering from a bout of ITBS, which makes some sense. Although this episode has come on rather suddenly, I was suffering from a bit of pain in my left leg/knee prior to this flareup. It may be a combination of some strain on the ligaments as well.
I'm easing into some ITBS stretches, medicating with Advil, and enforcing rest until Monday. I even skipped this morning's swim class, something I rarely do. I just need to approach this as seriously as I've been approaching training, then get my schedule reordered so that I have more rest opportunities. With luck I'll be back on track relatively soon, without losing any fitness.
And there's still plenty of time before my first event of the season, in Luray.