Today's recovery run was important. The real deal, however, is how it was important. If you ask most runners, recovery runs are done to bounce back from, recover from yesterday's hard work out. They are meant to clear out lactic acid, get some resting miles in. Most athletes, even some coaches, would tell you this. However, it is not the case. The, "Matt Fitzgerald," running guru, genius, mad professional breaks it down in this article.
The real benefit, according to Matt and the research behind him, is that you are logging miles in a pre-fatigued state. Yesterday's long run wore you out, now you are making those worn out muscles work for you during the recovery run. Working hard when you are at a less than optimal level builds fitness.
Elites will often do this by racing during a big week. If there is a goal race in the near future, some Pros will run a race during a week with high mileage and no taper, specifically for the fitness benefit.
As Matt goes on to say in the article, there are no specifics to your speed or duration of your recovery run, simple figure it out for yourself.
For me, I ran 6 miles today on my tired legs at a pace of about 8:17/mile. I felt tired and good all at once. For the week, I have 23.5 miles in, with 2 more workouts to go.