The system of passing drills that comprise Mike McCarthy’s QB school work best with a trio of quarterbacks, the Pittsburgh Steelers coach explained Saturday at rookie minicamp.

“The ideal is to have three guys,” said McCarthy, who mentioned Drew Allar, Will Howard and Mason Rudolph as forming that trio once OTA workouts begin May 18.

What does that mean for Aaron Rodgers, who remained unsigned but was reportedly visiting Pittsburgh this weekend?

“I mean, three quarterbacks is the normal,” McCarthy said. “Four would be awesome.”

Still, there was no sign of Rodgers at UPMC Rooney Sports Complex on Saturday when the Steelers held the second day of rookie camp. Allar, a third-round draft pick from Penn State, was the only quarterback seen in the indoor practice facility, unless assistant coach Tom Arth still counts.

The 42-year-old Rodgers hasn’t yet revealed his career plans. However, McCarthy, Steelers owner Art Rooney II and general manager Omar Khan have described positive communications with the former MVP for the past four months.

Should Rodgers re-sign with the Steelers, he’d join a quarterback room that for now includes veteran backup Rudolph, second-year player Howard and rookie Allar.

“It’ll be great to have all three of those guys (at OTAs) because there’s a tempo to it,” McCarthy said of his practice drills. “In the quarterback room, the relationship of the quarterbacks in that room, that’s important. They spend a lot of time together. We have a lot of fundamental conversations that we need to get started. …

“I’m really looking forward to getting (Allar) in the room with Will and Mason.”