Ehh, it wasn't really a 4-3-3. It was 4-2-3-1 with a trequartista, which means Bastos was deeper and had more defensive responsibility. Pjanic or Delgado were the players in the hole.
Bastos in a 4-3-3 is sort of akin to Patrice Evra playing the left-flank of the 4-4-2.