Burnes (elbow) threw 20 pitches in a live batting practice session Friday, Alex Weiner of Arizona Sports reports.
This was Burnes' first session facing live hitters. He'll follow up with two innings and 35 pitches in a bridge game Tuesday. Diamondbacks manager Torey Lovullo indicated that Burnes is anxious to pitch in a real game, but the manager will hold off on that until sometime shortly after Sept. 1.