INDIANAPOLIS — The Giants know all too well how an innocuous neck injury can devolve into so much more — for example, the premature retirements of linebacker Antonio Pierce and running back David Wilson. There is concern that tight end Larry Donnell could be facing a similar fate.

Donnell missed the final eight games last season dealing with a neck issue. He insisted he felt no pain, but his MRI exam did not come back clean. He did not miss a game his first two years, breaking through with a 63-reception season in 2014. Undrafted out of Grambling State, Donnell has experienced problems with ball security, but he is a huge target at 6-foot-6 and has eight touchdown catches in his last 24 games.

On Thursday, general manager Jerry Reese said, ominously, Donnell has not yet received medical clearance to return to football activities.

“Hopefully he’ll be able to continue to play,’’ Reese said. “We’re expecting him to be back, but necks can be tricky. We’ll have to wait and see where that goes.

“We have a couple young tight ends on the roster that we like,’’ Reese added, referring to Will Tye and Matt LaCosse.

Reese said the Giants will “take extreme precaution’’ with Donnell.

Head coach Ben McAdoo on Wednesday said “absolutely’’ when asked if he expected Victor Cruz on the roster this season. Reese was not nearly as outspoken.

“Well, he is under contract right now, we’ll see where the process goes,’’ Reese said.

Packers GM Ted Thompson witnessed McAdoo’s formative years as an offensive assistant in the NFL and watched him ascend the ladder in Green Bay.

“[McAdoo] worked well with the quarterbacks,’’ Thompson said. “Good guy, good coach.’’

As far as how McAdoo will fare as the Giants’ head coach, Thompson said: “You never know how that’s going to work, you would think he’d be good at it. That’s not the easiest environment, probably in New York, but I’m from a little town in Texas, so I wouldn’t know.’’

Reese said new assistant GM Martin Mayhew, the former Lions general manager, “is completely qualified to do any job in the front office. We think he’ll bring a lot to the table for us.’’

Based on the collective bargaining agreement, every team has the option to carry over unused cap space from the previous year. Every team in the league opted to do so. The Giants have more unused cap space to carry over, $11.19 million, than all but five teams — the Jaguars (at nearly $33 million, the highest in the league), Browns, Raiders, 49ers and Titans. The league average for salary-cap carryover money is $6.4 million.

High carryover money usually equates to low success. The combined 2015 record of the six teams (including the Giants) with the most carryover money is 29-67.

The salary cap for now stands at $154 million. The Giants’ roster stood at $107 million — $47 million under the cap. Add in the $11 million in carryover money and the Giants have $58 million to spend. There is rampant speculation the salary cap for the 2016 season will inflate to as much as $160 million, boosting the Giants’ spending capability to $60 million.