Kevin Gilbride still is not sure why the Giants blew up their entire offensive system and plunked down a brand-new playbook on Eli Manning’s lap, when it should have been clear to everyone the issue wasn’t the system, it was the players running it.

“I didn’t quite understand making the quarterback make the adjustment they did,’’ Gilbride, the Giants’ former offensive coordinator, told The Post. “People knew what the problem was. You can’t ask that guy to stand here and take the pounding that he took last year. He solves problems with his brain and with his arm and to do that he’s got to have some protection. He’s not gonna solve it with his feet, he’s not that kind of quarterback.’’

Manning was the wrong kind of quarterback in 2013, and after his career-worst season, co-owner John Mara famously declared the offense “broken’’ and wholesale changes were made. Gilbride, no doubt about to get swept out, picked an opportune time to retire. Two of his longtime assistants, Jerald Ingram and Mike Pope, were not retained, others were reassigned and a slew of new coaching blood was hired, most notably Ben McAdoo, who had never before been an offensive coordinator, but earned high marks for his work in Green Bay with tight ends and quarterback Aaron Rodgers.

There is no disputing the Giants, operating McAdoo’s version of the West Coast offense, are far better this season than last, and while it is no longer broken, it is premature to declare the offense fixed. The Giants, 5-9 after 14 games for a second consecutive year, are in the middle of the pack in scoring at 22.6 points per game. They are 26th in yards per play, 29th in rushing yards per attempt, 14th in total offense (based only on yards per game, and thus misleading). With two games remaining, the Giants have 37 touchdowns on offense. Gilbride spent seven years as offensive coordinator, and his attack, starting in 2007, produced these touchdown totals: 38, 42, 42, 48, 46 and 44 before last year’s plummet to 29.

Rather than the league catching up to the Giants’ offense, Gilbride blames the 2013 decline on a roster sapped of talent. He had Andre Brown and Peyton Hillis as his primary running backs, a hobbled Hakeem Nicks making few plays at receiver, a tight end, Brandon Myers, who spent one year with the team and then was gone. He saw Chris Snee at right guard go down after two games, lost David Baas at center, witnessed Will Beatty endure a terrible season at left tackle, had to actually put James Brewer on the field at left guard and had to navigate through the last years in a Giants uniform for David Diehl (now a Fox analyst) and Kevin Boothe (not playing a lick for the Raiders).

All the proof needed to realize how low the gauge fell on the talent meter came last spring, when general manager Jerry Reese admitted — by deeds, not words — the roster was a mess with his uncharacteristic spending foray in free agency.

“They were trying to do the right thing,’’ Gilbride said. “There was a decision that ‘Hey, the talent level wasn’t where it needed to be’ and what did they spend, $110 million in the offseason?’’

Gilbride, 63, is enjoying seeing what life is like outside the grind of the coaching world. He lives in South Kingstown, R.I., separated from the ocean by a wildlife preserve. Instead of figuring out ways to score on Eagles, Seahawks, Falcons and Bears, Gilbride now has to contend with wild turkeys, coyotes, fisher cats and more. “I never thought I’d grow to hate deer, but once I saw the damage they do to your trees and shrubs and bushes — we got all the deer you could possibly want,’’ he said. “You name it, we got it. The only thing that bothers me is the ticks.’’

Last month, Gilbride was informed by his sister that this was the first time in 28 years he had spent Thanksgiving at her house.

“I’m enjoying being able to do some things I’ve never had a chance to do before,’’ he said. “All of a sudden life’s gone by and you haven’t been part of it.’’

He keeps his hand in football as an analyst on NBCSN’s Pro Football Talk, heading to the studio in Stamford, Conn., on Mondays and Fridays. It looks as if his former boss, Tom Coughlin, is going to return for a 12th season as head coach.

“I’m too close to it because I care too much about those coaches and worry about what would happen to them if there was a change made,” Gilbride said. “I just hope there’s a recognition of the job that’s been done by those guys and if there is then I think the right decision will be made.’’

What is the “right decision’’ in his mind?

“I’m not going to get into that,’’ Gilbride said. “I’m too close to that. That’s really wrong of me. I got a son on that staff. I’m very close to a lot of those people.’’

Gilbride’s son, Kevin M. Gilbride, is the Giants’ tight ends coach.

As for Coughlin, well, Gilbride knows the deal.

“The assistants are the ones teaching the X’s and O’s and looking at the scheme and the strategy that has to be done and Tom’s working his tail off making sure the atmosphere is what it needs to be so those guys are learning those lessons, absorbing them, continuing to compete and fight,’’ he said. “I have no doubt that has not waned at all.’’