It was hard enough for Peyton Hillis to believe he went from being idle one week to the Giants’ starting running back and the main bell cow on football’s primetime stage the next. And he’s liable to get even more work on Sunday in Philadelphia, with Brandon Jacobs listed as doubtful for the NFC East matchup with the Eagles.

“It was shocking and surreal at the same time, because a week ago I wasn’t doing anything, and then I was on “Monday Night Football” carrying the ball,” said Hillis, who was signed off the street last Wednesday and started in Big Blue’s 23-7 victory over Minnesota. “I expect that [the soreness] is going to be here for a couple more weeks, but I have to work through it and try to produce.’’

Hillis got cut by the Buccaneers a month ago and was home in Tennessee when he got the call from the Giants. He carried 18 times for just 36 yards, caught five passes for 45 more and seems certain to start after Jacobs missed his third straight practice on Friday.

Rookie Michael Cox is the Giants’ only other healthy running back, and still is slowly but surely earning the coaching staff’s trust. When offensive coordinator Kevin Gilbride was asked if he would try to baby Hillis since he had been inactive, Gilbride pointed out the team didn’t have other options.

“I don’t know if that’s good for me or bad for me,’’ Hillis chuckled.

Cox is a seventh-round pick out of UMass, and had his first 11 NFL carries Monday for 23 yards — but more importantly, had no glaring gaffes.