EAST RUTHERFORD, N.J. — Thursday provided the first glimpse of a John Harbaugh practice, as the New York Giants’ third OTA was open to the media. Aside from an extended special teams period to open practice — and no music being played outside of team periods — it didn’t look drastically different from any other NFL practice.The Giants worked in their indoor facility because of rainy conditions. Here are some notes and observations from my first viewing of a Harbaugh practice with the full 90-man roster:Taking attendanceAs always, it’s important to note OTAs are voluntary. But attendance is taken, and the following players weren’t spotted at Thursday’s practice: QB Jameis Winston, RB Cam Skattebo, FB Pat Ricard, DL DJ Reader, DL Shelby Harris, DL Sam Roberts and CB Dru Phillips.WR Darius Slayton (sports hernia surgery) and rookie CB Colton Hood (undisclosed) came out to practice late but didn’t participate. Skattebo (ankle), Nabers (knee) and Roberts (undisclosed) are recovering from documented surgeries. There was no word on the absences of Winston, Ricard, Reader, Harris or Phillips.Harbaugh’s update on Nabers, who recently underwent a second surgery to remove scar tissue from his knee, wasn’t particularly encouraging.“He’s in the middle of (his rehab),” Harbaugh said. “It’s such a hard thing. It’s an ACL and whatever else he had in that knee. Not a simple knee, you know. So he’s in the slog of it, the grind of it, I would say. So he’s fighting through it. He’s here every day, working hard at it. Just impossible to predict. I mean, the goal is to start the season and get out there sometime in training camp. That would be the goal. We’ll see what happens. If he’s out there, great. If he’s not out there, great. We’ll be ready to go either way.”That’s a far cry from previous updates this offseason when Harbaugh and general manager Joe Schoen expressed optimism that Nabers would be ready for the start of training camp.Harbaugh said Slayton had been trying to work through the sports hernia, but “we all agreed: just get it fixed.” Harbaugh said Slayton will be 100 percent for the start of camp.Injury reportDefensive lineman Roy Robertson-Harris limped off the field midway through practice. He left the practice field and went into the facility after trainers examined his right leg.