NFL

Giants’ receiver corps remains up in the air

The Giants already know who won’t be here.

A passing attack that clicked more often than it fizzled last season will operate without Kevin Boss, the reliable tight end who signed with the Raiders. Ramses Barden, a statuesque athlete and receiver, has yet to take the field at training camp, ankle surgery keeping him on the sideline and testing the patience of head coach Tom Coughlin, who yesterday finally snapped, saying, “Barden, get out there, for crying out loud!”

There’s also no sight or sound from Steve Smith, and that is troublesome. The savvy slot receiver, holder of the Giants franchise record for catches in a season (107 in 2009), remains unsigned. Coming off microfracture knee surgery, Smith saw his market value plummet, and it is probable he will return on a short-term deal. Even if he walks in the door tomorrow, Smith won’t be ready to practice — far from it.

“He’s not going to step in right away,” Coughlin said.

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More likely, Smith will need the entire preseason to get caught up, and it is a stretch to imagine he would be ready for the start of the season. It could be a game or two, or a month. Either way, Smith is not here and the Giants are installing an offense without him.

“I hope he comes back, but if he doesn’t I’m preparing myself as if I’m going to be in there the whole year,” Mario Manningham said.

“In there” is the slot receiver spot, a place where Manningham has never played, not in college at Michigan and not in his three years with the Giants. When three receivers are on the field — something that is called for more than half the time — Manningham was flanked outside, along with Hakeem Nicks, and Smith inside in the slot.

That threesome proved to be a deadly combination, with three disparate skill sets working off each other. Smith, with his crafty route-running, instinct for finding open space and soft hands, was Eli Manning’s security blanket and best first-down maker.

Manningham, who did not practice last night because of a slight ankle issue, started eight games last season filling in for Smith and set career highs in catches (60), yards (944), touchdowns (nine) and reception average (15.7). All the damage was done as an outside receiver, where he had more room to maneuver and less congestion to deal with. But thus far in camp, Manningham has lined up in the slot, with Nicks and Domenik Hixon — returning from reconstructive knee surgery — on the outside in the three-receiver set.

This is new for Manningham.

“I’m starting to get really used to being in the slot,” Manningham said. “I feel like if I lined up in the slot, I’m not going to say I would have the advantage, but it would be a nickel or a linebacker over me.”

That nickel back or linebacker, or defensive end dropping into coverage, has the assignment of bumping the slot receiver — and not gently. It’s no place for finesse until you break free of the traffic and then, crossing over the middle, a collision is a distinct possibility.

“Toughness is just heart, and I have heart,” Manningham said. “Most people are not used to seeing me get hit because I don’t get hit as often, but I’m sure the day will come when I take a nice, good licking. I’m going to get back up. That’s just how I am, that’s the fight in me.”

The entire dynamic of the receiver corps has changed due to Smith’s absence. Hixon and Victor Cruz are vying for the No. 3 spot, with rookie Jerrel Jernigan trying to make a push and veterans Devin Thomas and Michael Clayton searching for roster spots. Barden, whenever he returns, must show the progress he was just starting to make last season is real.

If the third option cannot emerge as a legitimate threat, defenses will be able to brazenly devote extra attention to Nicks.

“I’m probably a marked man,” Nicks said, expressing confidence that offensive coordinator Kevin Gilbride can move him around enough to make enough plays.

Coughlin said the preseason will be about “hoping that people come along.”

In other words: Get signed and get healthy soon, Steve Smith.

paul.schwartz@nypost.com