The Giants began defensive preparations for Sunday’s game expecting to face a right-handed pocket pᴀsser with 169 games of NFL experience.

Instead, they will face a left-handed rookie with better mobility but less insтιтutional knowledge gained from throwing just five career pᴀsses.

When the Falcons made a quarterback change Tuesday from Kirk Cousins to Michael Penix Jr., it meant that the Giants had to scrap what they thought they knew and watch college tape of Penix at Washington and review their own draft reports.

The first-round pick will make his first NFL start against the Giants.

“He can sling it,” defensive coordinator Shane Bowen said. “You go back and watch the accuracy throwing the ball down the field. He puts it in places receivers can catch it. We’re going to have to do a good job making sure we defend the deep part of the field because I think he’s going to take his chances launching it.”

The Giants never strongly considered using their first-round pick on Penix, who surprisingly was drafted No. 8 overall — two picks after they took Malik Nabers.

“You watch Washington, try to get a feel for him and see his strengths,” Bowen said. “Hopefully you can find some weaknesses, which is hard to do.”

The Giants are coming off allowing six plays of 20 yards or more to the Ravens as receivers ran open through their patchwork secondary.

“We can’t let guys free,” Bowen said, “and have to make sure we’re deep when we need to be deep and on the right guys at the right time.”

Penix is not a true dual threat — certainly not compared to last week’s challenge of Lamar Jackson — but that element can’t be ignored, either.

“If there’s space, he’s going to take off,” Bowen said. “Can’t give him big rush lanes down the middle for him to take and make it inviting for him. There’s obviously a little bit more mobility than what they had there previously [with Cousins].

Five players did not practice Thursday: LB Bobby Okereke (back), EDGE Brian Burns (ankle/neck), LB Patrick Johnson (knee), G Aaron Stinnie (concussion) and CB Greg Stroman (shoulder/shin).

Burns “should be ready to go for the game,” coach Brian Daboll said.

Six players who were limited in Wednesday’s practice were upgraded to full participants: QB Drew Lock (heel/left elbow), WR Malik Nabers (knee/foot), WR Wan’Dale Robinson (shoulder), TE Chris Manhertz (ankle), DL Cory Durden (shoulder) and S Dane Belton (knee).

Eight players remain limited: QB Tommy DeVito (concussion), RB Tyrone Tracy (ankle), C John Michael Schmitz (ankle), DL Rakeem Nunez-Roches (neck/shoulder), CB Tae Banks (rib), CB Cor’Dale Flott (quad/finger), CB Dru Phillips (shoulder) and CB Art Green (shoulder).

Daboll said that DeVito is “moving right along (through the protocol) and should be available.”

The Giants tried a new kick returner last week, using recently acquired CB Dee Williams in place of fumble-prone Eric Gray as the option next to Ihmir Smith-Marsette. The undrafted rookie had one 23-yard return and is expected to hold on to the spot Sunday.

“Just want to give a younger player in this league, who’s shown a skill set to do it, an opportunity,” special teams coordinator Michael Ghobrial said. “He definitely has the right skill set to do it — a lot of juice, speed, elusiveness.”