BOSTON — Nets star forward Ben Simmons participated in four-on-four drills on Monday and five-on-zero “scripting, running through the plays” on Tuesday with no setback to the lower back injury that has restricted him from making his Nets debut, head coach Steve Nash said after Tuesday’s practice at Harvard. “Yesterday was his first day of contact,” Nash said at the Lavietes Pavilion. “He played with some teammates yesterday and he’s making progress, but there’s no real update. We’ll just see how he responds and see if he’s able to do more contact tomorrow.” Asked how Simmons’ back responded to…