The NFL Draft starts on Thursday.

The defining work begins on Friday and continues into Saturday.

That’s when the “middle rounds” of the selection process will take place. Rounds 3 through 5. Players who are just a hair below their much-hyped counterparts, who might need a bit of development or a new system to thrive, are chosen at a faster pace, without a hug from the commissioner, on networks that end their call signs with the number 2.

It’s also the place the Giants have faltered the most in recent years, and the area in which the front office under Jerry Reese needs to see the most improvement if it is going to remain in place.

The Giants hold the 10th selection in the first round, which means however the draft shakes out, they will get a player they believe is a Top 10 pick. Those selections don’t always pan out, but certainly improve the chances of the team getting a winner.

And the Giants seem to have had a good run of recent first-rounders: Justin Pugh and Ereck Flowers are solid starters on the offensive line and Odell Beckham Jr. is a transcendent playmaker. The Giants have even done pretty well for themselves with their last three second-rounders: Johnathan Hankins, Weston Richburg and Landon Collins.

advertisement | advertise on newsday

Again, though, those picks are batting-practice pitches. Grooved not-so-fastballs. All of them were taken in the Top 50 picks. They were supposed to be home runs. Anyone with an Internet connection and a few bucks to spend on draft publications reasonably would have done just as well.

The rest of the draft picks since, well, 2008? Reese and the Giants almost have an oh-fer.

Linebacker Devon Kennard is the one saving pick in that lot as a fifth-rounder in 2014 who has become an impact player and regular starter. But even he has some questions hovering around him regarding injuries as he enters his third season.

The only pick in that group who has given the Giants exactly what they expected on a consistent basis is Ryan Nassib, the backup quarterback taken in the fourth round of 2013, with Reese hoping he would never have to play.

Mission accomplished!

Giants videos

The rest of the lot of third- through fifth-rounders in the past seven drafts is littered with disappointing names such as Ramses Barden, Travis Beckum, Phillip Dillard, Jerrell Jernigan, Adrien Robinson and Damontre Moore.

Some of it has been bad luck. Injuries ended the career of Chad Jones and Andre Brown and so far have stunted the growth of Nat Berhe, Owa Odighizuwa and Mykkele Thompson. Ideally, some of those players should now represent the core of the Giants’ roster. Instead, most of them are watching the Red Zone channel on Sundays for a glimpse of what might have been.

The question is: Why have the Giants struggled in these middle rounds?

“We looked at a lot of things,” Reese said. “I’m not going to sit here and divulge what we talked about and what we discovered and what we looked at, but we worked hard on some things. I know this. I know our scouts work their behinds off. They do all of the work. They’re on the road for almost 200 days out of the year. They do the legwork for us and they do a tremendous job for us.”

Asked again to describe the findings and changes the Giants will be making for those middle rounds, Reese dodged the question like a presidential candidate.

advertisement | advertise on newsday

“There’s always things that you find interesting when you do some research, and there were some interesting things that we found,” he said.

Looking back on the two recent Giants championship teams, it’s easy to see where this current edition differs. Those squads were led mostly by middle-round picks. Sure, the MVP of both Super Bowl XLII and XLVI was a first-round choice (not Reese’s, and technically not even the Giants’) in Eli Manning. But David Diehl (fifth), Justin Tuck (third), Brandon Jacobs (fourth), Barry Cofield (fourth), Ahmad Bradshaw (seventh) and Mario Manningham (third) all came from that fruitful ground in the middle of the draft that the Giants have not been harvesting of late.

So tune in on Thursday to see whom the Giants select in the first round. Compare it to the mock drafts. Project how that player will fit into the 2016 scheme. But stay tuned on Friday and Saturday for players you might have never heard of, who aren’t on magazine covers, who might be selected during commercial breaks, with their big announcements relegated to the ticker at the bottom of the screen.

When Tuck was drafted in 2005, reporters didn’t even bother to get him on a conference call. This fall, he might be inducted into the Ring of Honor at MetLife Stadium.

The middle rounds are where a team can truly help itself. That’s where this Giants draft will be graded several years from now.

advertisement | advertise on newsday

They are the lifeblood of organizations.

And the Giants are in dire need of a transfusion.