Urias' move raised some eyebrows in the Washington dugout, though. According to Rule 8.05, "If a left-handed or right-handed pitcher swings his free foot past the back edge of the pitcher's rubber, he is required to pitch to the batter except to throw to second base on a pick-off play."
Urias' free foot certainly came close to crossing that imaginary line. But in the eyes of the umpiring crew, it was a clean throw to first base and not a balk.
Earlier in the frame, Urias struck out Nationals pitcher Max Scherzer before getting Trea Turner to bounce back to the mound.