NFL

Giants WR Smith out for season with knee injury

Mario Manningham (Joseph E. Amaturo)

For the past month, the starting receiver situation for the Giants has been a week-to-week deal. There was certainty affixed to the position yesterday, but it was not the news the Giants wanted to learn.

The stretch run of the season will go on without Steve Smith, widely considered the team’s most reliable receiver and a wizard in the slot as Eli Manning’s favorite target. What at first was thought to be a hamstring injury coming out of last Monday night’s 21-3 victory over the Vikings has been diagnosed as damage to the articular cartilage in his left knee. Smith needs surgery, his season is over — playoffs included — and he will be placed on injured reserve.

“Very deflating,” receiver Hakeem Nicks said.

This is not the way the Giants envisioned heading into the most important week of the season as they get ready for Sunday’s NFC East first-place showdown with the Eagles.

“Hopefully we can help Steve over this great disappointment for him, and our team just has to march on,” coach Tom Coughlin said.

Mario Manningham steps into the starting role, but he did not play in the second half against the Vikings because of an injury to his hip flexor. He still is hurting and is unsure how much he will be able to practice this week but vowed to be on the field this weekend. He was able to participate in yesterday’s light walk-through workout.

“I’ll be all right,” Manningham said. “Trust me, I’ll be good to go Sunday at 1 o’clock.”

Smith will not be good to go for quite some time. The articular cartilage is smooth white tissue that covers the end of bones. When damaged, it does not regenerate and one of the options is microfracture surgery, which would necessitate a lengthy rehabilitation and could put in question his return for the start of next season.

The Giants were forced to run their offense without Smith for an entire month while he recovered from a partially torn pectoral muscle. They welcomed him back last week, and he caught just one pass — a 12-yard completion in the third quarter — and immediately was pulled down from behind by linebacker Chad Greenway, causing Smith’s left knee to hyperextend. He will become the fifth Giants receiver to be put on injured reserve this season.

“It’s unfortunate, but you can’t dwell on it,” Manning said. “We got other receivers. We have guys who can make big plays for us. These last few weeks we’ve been without him and been able to win some games. We know we can win.”

Smith is second on the team with 48 receptions for 529 yards and three touchdowns and runs the most consistent routes on the team. He is the perfect partner for Nicks, because both receivers can exploit single coverage.

“I wish the best for him, pray for a speedy recovery for him,” Nicks said. “His presence will definitely be missed in that slot, on third down situations and other situations as well.”

Without Smith, Manningham’s health grows in importance. The Giants have added Derek Hagan, Michael Clayton and Devin Thomas during the season, but it is unlikely Clayton or Thomas will be able to provide much of an offensive spark. Hagan moves up into the No. 3 spot and likely will see most of his action as the slot receiver in the three-wide package.

Manningham said he hurt himself in the second quarter on Brandon Jacobs’ 73-yard run. Manningham was running downfield chasing after cornerback Antonio Winfield, and he felt “a little pull.” Manningham said he could not have continued to play, but insists he will be able to make it this Sunday and be able to hold down the fort without Smith.

“There have been a lot of injuries this year. It’s another injury we have in our receiving group,” Manningham said. “I don’t really feel any pressure. I have to work harder, I have to watch more film, just prepare myself harder knowing I’m going to play that position for the whole game for the rest of the year.”

paul.schwartz@nypost.com